Calculus Examples

$f (x) = \frac{\sqrt{9 x^{2} + 1}}{x}$

Step 1

Find the $x$ values where the second derivative is equal to $0$ .

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Step 1.1

Find the second derivative.

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Step 1.1.1

Find the first derivative.

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Step 1.1.1.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{9 x^{2} + 1}$ as ${(9 x^{2} + 1)}^{\frac{1}{2}}$ .

$\frac{d}{d x} [\frac{{(9 x^{2} + 1)}^{\frac{1}{2}}}{x}]$

Step 1.1.1.2

Differentiate using the Quotient Rule which states that $\frac{d}{d x} [\frac{f (x)}{g (x)}]$ is $\frac{g (x) \frac{d}{d x} [f (x)] - f (x) \frac{d}{d x} [g (x)]}{{g (x)}^{2}}$ where $f (x) = {(9 x^{2} + 1)}^{\frac{1}{2}}$ and $g (x) = x$ .

$\frac{x \frac{d}{d x} [{(9 x^{2} + 1)}^{\frac{1}{2}}] - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{\frac{1}{2}}$ and $g (x) = 9 x^{2} + 1$ .

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Step 1.1.1.3.1

To apply the Chain Rule, set $u$ as $9 x^{2} + 1$ .

$\frac{x (\frac{d}{d u} [u^{\frac{1}{2}}] \frac{d}{d x} [9 x^{2} + 1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.3.2

Differentiate using the Power Rule which states that $\frac{d}{d u} [u^{n}]$ is $n u^{n - 1}$ where $n = \frac{1}{2}$ .

$\frac{x (\frac{1}{2} u^{\frac{1}{2} - 1} \frac{d}{d x} [9 x^{2} + 1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.3.3

Replace all occurrences of $u$ with $9 x^{2} + 1$ .

$\frac{x (\frac{1}{2} {(9 x^{2} + 1)}^{\frac{1}{2} - 1} \frac{d}{d x} [9 x^{2} + 1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.4

To write $- 1$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

$\frac{x (\frac{1}{2} {(9 x^{2} + 1)}^{\frac{1}{2} - 1 \cdot \frac{2}{2}} \frac{d}{d x} [9 x^{2} + 1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.5

Combine $- 1$ and $\frac{2}{2}$ .

$\frac{x (\frac{1}{2} {(9 x^{2} + 1)}^{\frac{1}{2} + \frac{- 1 \cdot 2}{2}} \frac{d}{d x} [9 x^{2} + 1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.6

Combine the numerators over the common denominator.

$\frac{x (\frac{1}{2} {(9 x^{2} + 1)}^{\frac{1 - 1 \cdot 2}{2}} \frac{d}{d x} [9 x^{2} + 1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.7

Simplify the numerator.

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Step 1.1.1.7.1

Multiply $- 1$ by $2$ .

$\frac{x (\frac{1}{2} {(9 x^{2} + 1)}^{\frac{1 - 2}{2}} \frac{d}{d x} [9 x^{2} + 1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.7.2

Subtract $2$ from $1$ .

$\frac{x (\frac{1}{2} {(9 x^{2} + 1)}^{\frac{- 1}{2}} \frac{d}{d x} [9 x^{2} + 1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.8

Combine fractions.

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Step 1.1.1.8.1

Move the negative in front of the fraction.

$\frac{x (\frac{1}{2} {(9 x^{2} + 1)}^{- \frac{1}{2}} \frac{d}{d x} [9 x^{2} + 1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.8.2

Combine $\frac{1}{2}$ and ${(9 x^{2} + 1)}^{- \frac{1}{2}}$ .

$\frac{x (\frac{{(9 x^{2} + 1)}^{- \frac{1}{2}}}{2} \frac{d}{d x} [9 x^{2} + 1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.8.3

Move ${(9 x^{2} + 1)}^{- \frac{1}{2}}$ to the denominator using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$\frac{x (\frac{1}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [9 x^{2} + 1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.8.4

Combine $\frac{1}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}}$ and $x$ .

$\frac{\frac{x}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [9 x^{2} + 1] - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.9

By the Sum Rule, the derivative of $9 x^{2} + 1$ with respect to $x$ is $\frac{d}{d x} [9 x^{2}] + \frac{d}{d x} [1]$ .

$\frac{\frac{x}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} (\frac{d}{d x} [9 x^{2}] + \frac{d}{d x} [1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.10

Since $9$ is constant with respect to $x$ , the derivative of $9 x^{2}$ with respect to $x$ is $9 \frac{d}{d x} [x^{2}]$ .

$\frac{\frac{x}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} (9 \frac{d}{d x} [x^{2}] + \frac{d}{d x} [1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.11

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

$\frac{\frac{x}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} (9 (2 x) + \frac{d}{d x} [1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.12

Multiply $2$ by $9$ .

$\frac{\frac{x}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} (18 x + \frac{d}{d x} [1]) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.13

Since $1$ is constant with respect to $x$ , the derivative of $1$ with respect to $x$ is $0$ .

$\frac{\frac{x}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} (18 x + 0) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.14

Combine fractions.

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Step 1.1.1.14.1

Add $18 x$ and $0$ .

$\frac{\frac{x}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} (18 x) - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.14.2

Combine $18$ and $\frac{x}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}}$ .

$\frac{\frac{18 x}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} x - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.14.3

Combine $\frac{18 x}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}}$ and $x$ .

$\frac{\frac{18 x \cdot x}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.15

Raise $x$ to the power of $1$ .

$\frac{\frac{18 (x^{1} x)}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.16

Raise $x$ to the power of $1$ .

$\frac{\frac{18 (x^{1} x^{1})}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.17

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{\frac{18 x^{1 + 1}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.18

Add $1$ and $1$ .

$\frac{\frac{18 x^{2}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.19

Factor $2$ out of $18 x^{2}$ .

$\frac{\frac{2 (9 x^{2})}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.20

Cancel the common factors.

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Step 1.1.1.20.1

Factor $2$ out of $2 {(9 x^{2} + 1)}^{\frac{1}{2}}$ .

$\frac{\frac{2 (9 x^{2})}{2 ({(9 x^{2} + 1)}^{\frac{1}{2}})} - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.20.2

Cancel the common factor.

$\frac{\frac{2 (9 x^{2})}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.20.3

Rewrite the expression.

$\frac{\frac{9 x^{2}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.21

Multiply $\frac{\frac{9 x^{2}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$ by $\frac{{(9 x^{2} + 1)}^{\frac{1}{2}}}{{(9 x^{2} + 1)}^{\frac{1}{2}}}$ .

$\frac{{(9 x^{2} + 1)}^{\frac{1}{2}}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} \cdot \frac{\frac{9 x^{2}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x]}{x^{2}}$

Step 1.1.1.22

Combine.

$\frac{{(9 x^{2} + 1)}^{\frac{1}{2}} (\frac{9 x^{2}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} - {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x])}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.23

Apply the distributive property.

$\frac{{(9 x^{2} + 1)}^{\frac{1}{2}} \frac{9 x^{2}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + {(9 x^{2} + 1)}^{\frac{1}{2}} (- {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x])}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.24

Cancel the common factor of ${(9 x^{2} + 1)}^{\frac{1}{2}}$ .

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Step 1.1.1.24.1

Cancel the common factor.

Step 1.1.1.24.2

Rewrite the expression.

$\frac{9 x^{2} + {(9 x^{2} + 1)}^{\frac{1}{2}} (- {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x])}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.25

Multiply ${(9 x^{2} + 1)}^{\frac{1}{2}}$ by ${(9 x^{2} + 1)}^{\frac{1}{2}}$ by adding the exponents.

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Step 1.1.1.25.1

Move ${(9 x^{2} + 1)}^{\frac{1}{2}}$ .

$\frac{9 x^{2} + {(9 x^{2} + 1)}^{\frac{1}{2}} {(9 x^{2} + 1)}^{\frac{1}{2}} (- \frac{d}{d x} [x])}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.25.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{9 x^{2} + {(9 x^{2} + 1)}^{\frac{1}{2} + \frac{1}{2}} (- \frac{d}{d x} [x])}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.25.3

Combine the numerators over the common denominator.

$\frac{9 x^{2} + {(9 x^{2} + 1)}^{\frac{1 + 1}{2}} (- \frac{d}{d x} [x])}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.25.4

Add $1$ and $1$ .

$\frac{9 x^{2} + {(9 x^{2} + 1)}^{\frac{2}{2}} (- \frac{d}{d x} [x])}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.25.5

Divide $2$ by $2$ .

$\frac{9 x^{2} + {(9 x^{2} + 1)}^{1} (- \frac{d}{d x} [x])}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.26

Simplify ${(9 x^{2} + 1)}^{1} (- \frac{d}{d x} [x])$ .

$\frac{9 x^{2} + (9 x^{2} + 1) (- \frac{d}{d x} [x])}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.27

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$\frac{9 x^{2} + (9 x^{2} + 1) (- 1 \cdot 1)}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.28

Simplify the expression.

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Step 1.1.1.28.1

Multiply $- 1$ by $1$ .

$\frac{9 x^{2} + (9 x^{2} + 1) \cdot - 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.28.2

Move $- 1$ to the left of $9 x^{2} + 1$ .

$\frac{9 x^{2} - 1 \cdot (9 x^{2} + 1)}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.28.3

Rewrite $- 1 (9 x^{2} + 1)$ as $- (9 x^{2} + 1)$ .

$\frac{9 x^{2} - (9 x^{2} + 1)}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.29

Simplify.

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Step 1.1.1.29.1

Apply the distributive property.

$\frac{9 x^{2} - (9 x^{2}) - 1 \cdot 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.29.2

Simplify the numerator.

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Step 1.1.1.29.2.1

Simplify each term.

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Step 1.1.1.29.2.1.1

Multiply $9$ by $- 1$ .

$\frac{9 x^{2} - 9 x^{2} - 1 \cdot 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.29.2.1.2

Multiply $- 1$ by $1$ .

$\frac{9 x^{2} - 9 x^{2} - 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.29.2.2

Subtract $9 x^{2}$ from $9 x^{2}$ .

$\frac{0 - 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.29.2.3

Subtract $1$ from $0$ .

$\frac{- 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.29.3

Move the negative in front of the fraction.

$- \frac{1}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$

Step 1.1.1.29.4

Reorder factors in $- \frac{1}{{(9 x^{2} + 1)}^{\frac{1}{2}} x^{2}}$ .

$f' (x) = - \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}}$

Step 1.1.2

Find the second derivative.

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Step 1.1.2.1

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = - 1$ and $g (x) = \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}}$ .

$- \frac{d}{d x} [\frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}}] + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.2

Rewrite $\frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}}$ as ${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 1}$ .

$- \frac{d}{d x} [{(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 1}] + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{- 1}$ and $g (x) = x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}$ .

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Step 1.1.2.3.1

To apply the Chain Rule, set $u_{1}$ as $x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}$ .

$- (\frac{d}{d u_{1}} [{u_{1}}^{- 1}] \frac{d}{d x} [x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.3.2

Differentiate using the Power Rule which states that $\frac{d}{d u_{1}} [{u_{1}}^{n}]$ is $n {u_{1}}^{n - 1}$ where $n = - 1$ .

$- (- {u_{1}}^{- 2} \frac{d}{d x} [x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.3.3

Replace all occurrences of $u_{1}$ with $x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}$ .

$- (- {(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} \frac{d}{d x} [x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.4

Multiply.

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Step 1.1.2.4.1

Multiply $- 1$ by $- 1$ .

$1 ({(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} \frac{d}{d x} [x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.4.2

Multiply ${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2}$ by $1$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} \frac{d}{d x} [x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}] + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.5

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x^{2}$ and $g (x) = {(9 x^{2} + 1)}^{\frac{1}{2}}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (x^{2} \frac{d}{d x} [{(9 x^{2} + 1)}^{\frac{1}{2}}] + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.6

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{\frac{1}{2}}$ and $g (x) = 9 x^{2} + 1$ .

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Step 1.1.2.6.1

To apply the Chain Rule, set $u_{2}$ as $9 x^{2} + 1$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (x^{2} (\frac{d}{d u_{2}} [{u_{2}}^{\frac{1}{2}}] \frac{d}{d x} [9 x^{2} + 1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.6.2

Differentiate using the Power Rule which states that $\frac{d}{d u_{2}} [{u_{2}}^{n}]$ is $n {u_{2}}^{n - 1}$ where $n = \frac{1}{2}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (x^{2} (\frac{1}{2} {u_{2}}^{\frac{1}{2} - 1} \frac{d}{d x} [9 x^{2} + 1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.6.3

Replace all occurrences of $u_{2}$ with $9 x^{2} + 1$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (x^{2} (\frac{1}{2} {(9 x^{2} + 1)}^{\frac{1}{2} - 1} \frac{d}{d x} [9 x^{2} + 1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.7

To write $- 1$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (x^{2} (\frac{1}{2} {(9 x^{2} + 1)}^{\frac{1}{2} - 1 \cdot \frac{2}{2}} \frac{d}{d x} [9 x^{2} + 1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.8

Combine $- 1$ and $\frac{2}{2}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (x^{2} (\frac{1}{2} {(9 x^{2} + 1)}^{\frac{1}{2} + \frac{- 1 \cdot 2}{2}} \frac{d}{d x} [9 x^{2} + 1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.9

Combine the numerators over the common denominator.

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (x^{2} (\frac{1}{2} {(9 x^{2} + 1)}^{\frac{1 - 1 \cdot 2}{2}} \frac{d}{d x} [9 x^{2} + 1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.10

Simplify the numerator.

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Step 1.1.2.10.1

Multiply $- 1$ by $2$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (x^{2} (\frac{1}{2} {(9 x^{2} + 1)}^{\frac{1 - 2}{2}} \frac{d}{d x} [9 x^{2} + 1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.10.2

Subtract $2$ from $1$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (x^{2} (\frac{1}{2} {(9 x^{2} + 1)}^{\frac{- 1}{2}} \frac{d}{d x} [9 x^{2} + 1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.11

Combine fractions.

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Step 1.1.2.11.1

Move the negative in front of the fraction.

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (x^{2} (\frac{1}{2} {(9 x^{2} + 1)}^{- \frac{1}{2}} \frac{d}{d x} [9 x^{2} + 1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.11.2

Combine $\frac{1}{2}$ and ${(9 x^{2} + 1)}^{- \frac{1}{2}}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (x^{2} (\frac{{(9 x^{2} + 1)}^{- \frac{1}{2}}}{2} \frac{d}{d x} [9 x^{2} + 1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.11.3

Move ${(9 x^{2} + 1)}^{- \frac{1}{2}}$ to the denominator using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (x^{2} (\frac{1}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [9 x^{2} + 1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.11.4

Combine $\frac{1}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}}$ and $x^{2}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{x^{2}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [9 x^{2} + 1] + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.12

By the Sum Rule, the derivative of $9 x^{2} + 1$ with respect to $x$ is $\frac{d}{d x} [9 x^{2}] + \frac{d}{d x} [1]$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{x^{2}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} (\frac{d}{d x} [9 x^{2}] + \frac{d}{d x} [1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.13

Since $9$ is constant with respect to $x$ , the derivative of $9 x^{2}$ with respect to $x$ is $9 \frac{d}{d x} [x^{2}]$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{x^{2}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} (9 \frac{d}{d x} [x^{2}] + \frac{d}{d x} [1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.14

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{x^{2}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} (9 (2 x) + \frac{d}{d x} [1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.15

Multiply $2$ by $9$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{x^{2}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} (18 x + \frac{d}{d x} [1]) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.16

Since $1$ is constant with respect to $x$ , the derivative of $1$ with respect to $x$ is $0$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{x^{2}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} (18 x + 0) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.17

Combine fractions.

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Step 1.1.2.17.1

Add $18 x$ and $0$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{x^{2}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} (18 x) + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.17.2

Combine $18$ and $\frac{x^{2}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{18 x^{2}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} x + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.17.3

Combine $\frac{18 x^{2}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}}$ and $x$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{18 x^{2} x}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.18

Raise $x$ to the power of $1$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{18 (x^{1} x^{2})}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.19

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{18 x^{1 + 2}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.20

Add $1$ and $2$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{18 x^{3}}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.21

Factor $2$ out of $18 x^{3}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{2 (9 x^{3})}{2 {(9 x^{2} + 1)}^{\frac{1}{2}}} + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.22

Cancel the common factors.

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Step 1.1.2.22.1

Factor $2$ out of $2 {(9 x^{2} + 1)}^{\frac{1}{2}}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{2 (9 x^{3})}{2 ({(9 x^{2} + 1)}^{\frac{1}{2}})} + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.22.2

Cancel the common factor.

Step 1.1.2.22.3

Rewrite the expression.

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{9 x^{3}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + {(9 x^{2} + 1)}^{\frac{1}{2}} \frac{d}{d x} [x^{2}]) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.23

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{9 x^{3}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + {(9 x^{2} + 1)}^{\frac{1}{2}} (2 x)) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.24

Move $2$ to the left of ${(9 x^{2} + 1)}^{\frac{1}{2}}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{9 x^{3}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + 2 \cdot {(9 x^{2} + 1)}^{\frac{1}{2}} x) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.25

Combine $\frac{9 x^{3}}{{(9 x^{2} + 1)}^{\frac{1}{2}}}$ and $2 {(9 x^{2} + 1)}^{\frac{1}{2}} x$ using a common denominator.

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Step 1.1.2.25.1

Move ${(9 x^{2} + 1)}^{\frac{1}{2}}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{9 x^{3}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + 2 x {(9 x^{2} + 1)}^{\frac{1}{2}}) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.25.2

To write $2 x {(9 x^{2} + 1)}^{\frac{1}{2}}$ as a fraction with a common denominator, multiply by $\frac{{(9 x^{2} + 1)}^{\frac{1}{2}}}{{(9 x^{2} + 1)}^{\frac{1}{2}}}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (\frac{9 x^{3}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + \frac{2 x {(9 x^{2} + 1)}^{\frac{1}{2}} {(9 x^{2} + 1)}^{\frac{1}{2}}}{{(9 x^{2} + 1)}^{\frac{1}{2}}}) + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.25.3

Combine the numerators over the common denominator.

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} \frac{9 x^{3} + 2 x {(9 x^{2} + 1)}^{\frac{1}{2}} {(9 x^{2} + 1)}^{\frac{1}{2}}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.26

Multiply ${(9 x^{2} + 1)}^{\frac{1}{2}}$ by ${(9 x^{2} + 1)}^{\frac{1}{2}}$ by adding the exponents.

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Step 1.1.2.26.1

Move ${(9 x^{2} + 1)}^{\frac{1}{2}}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} \frac{9 x^{3} + 2 x ({(9 x^{2} + 1)}^{\frac{1}{2}} {(9 x^{2} + 1)}^{\frac{1}{2}})}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.26.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} \frac{9 x^{3} + 2 x {(9 x^{2} + 1)}^{\frac{1}{2} + \frac{1}{2}}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.26.3

Combine the numerators over the common denominator.

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} \frac{9 x^{3} + 2 x {(9 x^{2} + 1)}^{\frac{1 + 1}{2}}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.26.4

Add $1$ and $1$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} \frac{9 x^{3} + 2 x {(9 x^{2} + 1)}^{\frac{2}{2}}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.26.5

Divide $2$ by $2$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} \frac{9 x^{3} + 2 x {(9 x^{2} + 1)}^{1}}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.27

Combine fractions.

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Step 1.1.2.27.1

Simplify $2 x {(9 x^{2} + 1)}^{1}$ .

${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} \frac{9 x^{3} + 2 x (9 x^{2} + 1)}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.27.2

Combine ${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2}$ and $\frac{9 x^{3} + 2 x (9 x^{2} + 1)}{{(9 x^{2} + 1)}^{\frac{1}{2}}}$ .

$\frac{{(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2} (9 x^{3} + 2 x (9 x^{2} + 1))}{{(9 x^{2} + 1)}^{\frac{1}{2}}} + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.27.3

Move ${(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{- 2}$ to the denominator using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$\frac{9 x^{3} + 2 x (9 x^{2} + 1)}{{(9 x^{2} + 1)}^{\frac{1}{2}} {(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{2}} + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \frac{d}{d x} [- 1]$

Step 1.1.2.28

Since $- 1$ is constant with respect to $x$ , the derivative of $- 1$ with respect to $x$ is $0$ .

$\frac{9 x^{3} + 2 x (9 x^{2} + 1)}{{(9 x^{2} + 1)}^{\frac{1}{2}} {(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{2}} + \frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}} \cdot 0$

Step 1.1.2.29

Simplify the expression.

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Step 1.1.2.29.1

Multiply $\frac{1}{x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}}$ by $0$ .

$\frac{9 x^{3} + 2 x (9 x^{2} + 1)}{{(9 x^{2} + 1)}^{\frac{1}{2}} {(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{2}} + 0$

Step 1.1.2.29.2

Add $\frac{9 x^{3} + 2 x (9 x^{2} + 1)}{{(9 x^{2} + 1)}^{\frac{1}{2}} {(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{2}}$ and $0$ .

$\frac{9 x^{3} + 2 x (9 x^{2} + 1)}{{(9 x^{2} + 1)}^{\frac{1}{2}} {(x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}})}^{2}}$

Step 1.1.2.30

Simplify.

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Step 1.1.2.30.1

Apply the product rule to $x^{2} {(9 x^{2} + 1)}^{\frac{1}{2}}$ .

$\frac{9 x^{3} + 2 x (9 x^{2} + 1)}{{(9 x^{2} + 1)}^{\frac{1}{2}} ({(x^{2})}^{2} {({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2})}$

Step 1.1.2.30.2

Apply the distributive property.

$\frac{9 x^{3} + 2 x (9 x^{2}) + 2 x \cdot 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} ({(x^{2})}^{2} {({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2})}$

Step 1.1.2.30.3

Simplify the numerator.

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Step 1.1.2.30.3.1

Simplify each term.

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Step 1.1.2.30.3.1.1

Rewrite using the commutative property of multiplication.

$\frac{9 x^{3} + 2 \cdot 9 x \cdot x^{2} + 2 x \cdot 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} ({(x^{2})}^{2} {({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2})}$

Step 1.1.2.30.3.1.2

Multiply $x$ by $x^{2}$ by adding the exponents.

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Step 1.1.2.30.3.1.2.1

Move $x^{2}$ .

$\frac{9 x^{3} + 2 \cdot 9 (x^{2} x) + 2 x \cdot 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} ({(x^{2})}^{2} {({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2})}$

Step 1.1.2.30.3.1.2.2

Multiply $x^{2}$ by $x$ .

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Step 1.1.2.30.3.1.2.2.1

Raise $x$ to the power of $1$ .

$\frac{9 x^{3} + 2 \cdot 9 (x^{2} x^{1}) + 2 x \cdot 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} ({(x^{2})}^{2} {({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2})}$

Step 1.1.2.30.3.1.2.2.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{9 x^{3} + 2 \cdot 9 x^{2 + 1} + 2 x \cdot 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} ({(x^{2})}^{2} {({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2})}$

Step 1.1.2.30.3.1.2.3

Add $2$ and $1$ .

$\frac{9 x^{3} + 2 \cdot 9 x^{3} + 2 x \cdot 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} ({(x^{2})}^{2} {({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2})}$

Step 1.1.2.30.3.1.3

Multiply $2$ by $9$ .

$\frac{9 x^{3} + 18 x^{3} + 2 x \cdot 1}{{(9 x^{2} + 1)}^{\frac{1}{2}} ({(x^{2})}^{2} {({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2})}$

Step 1.1.2.30.3.1.4

Multiply $2$ by $1$ .

$\frac{9 x^{3} + 18 x^{3} + 2 x}{{(9 x^{2} + 1)}^{\frac{1}{2}} ({(x^{2})}^{2} {({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2})}$

Step 1.1.2.30.3.2

Add $9 x^{3}$ and $18 x^{3}$ .

$\frac{27 x^{3} + 2 x}{{(9 x^{2} + 1)}^{\frac{1}{2}} ({(x^{2})}^{2} {({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2})}$

Step 1.1.2.30.4

Combine terms.

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Step 1.1.2.30.4.1

Multiply the exponents in ${(x^{2})}^{2}$ .

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Step 1.1.2.30.4.1.1

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$\frac{27 x^{3} + 2 x}{{(9 x^{2} + 1)}^{\frac{1}{2}} (x^{2 \cdot 2} {({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2})}$

Step 1.1.2.30.4.1.2

Multiply $2$ by $2$ .

$\frac{27 x^{3} + 2 x}{{(9 x^{2} + 1)}^{\frac{1}{2}} (x^{4} {({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2})}$

Step 1.1.2.30.4.2

Multiply the exponents in ${({(9 x^{2} + 1)}^{\frac{1}{2}})}^{2}$ .

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Step 1.1.2.30.4.2.1

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$\frac{27 x^{3} + 2 x}{{(9 x^{2} + 1)}^{\frac{1}{2}} (x^{4} {(9 x^{2} + 1)}^{\frac{1}{2} \cdot 2})}$

Step 1.1.2.30.4.2.2

Cancel the common factor of $2$ .

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Step 1.1.2.30.4.2.2.1

Cancel the common factor.

$\frac{27 x^{3} + 2 x}{{(9 x^{2} + 1)}^{\frac{1}{2}} (x^{4} {(9 x^{2} + 1)}^{\frac{1}{2} \cdot 2})}$

Step 1.1.2.30.4.2.2.2

Rewrite the expression.

$\frac{27 x^{3} + 2 x}{{(9 x^{2} + 1)}^{\frac{1}{2}} (x^{4} {(9 x^{2} + 1)}^{1})}$

Step 1.1.2.30.4.3

Simplify.

$\frac{27 x^{3} + 2 x}{{(9 x^{2} + 1)}^{\frac{1}{2}} (x^{4} (9 x^{2} + 1))}$

Step 1.1.2.30.4.4

Multiply ${(9 x^{2} + 1)}^{\frac{1}{2}}$ by $9 x^{2} + 1$ by adding the exponents.

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Step 1.1.2.30.4.4.1

Move $9 x^{2} + 1$ .

$\frac{27 x^{3} + 2 x}{(9 x^{2} + 1) {(9 x^{2} + 1)}^{\frac{1}{2}} x^{4}}$

Step 1.1.2.30.4.4.2

Multiply $9 x^{2} + 1$ by ${(9 x^{2} + 1)}^{\frac{1}{2}}$ .

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Step 1.1.2.30.4.4.2.1

Raise $9 x^{2} + 1$ to the power of $1$ .

$\frac{27 x^{3} + 2 x}{{(9 x^{2} + 1)}^{1} {(9 x^{2} + 1)}^{\frac{1}{2}} x^{4}}$

Step 1.1.2.30.4.4.2.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{27 x^{3} + 2 x}{{(9 x^{2} + 1)}^{1 + \frac{1}{2}} x^{4}}$

Step 1.1.2.30.4.4.3

Write $1$ as a fraction with a common denominator.

$\frac{27 x^{3} + 2 x}{{(9 x^{2} + 1)}^{\frac{2}{2} + \frac{1}{2}} x^{4}}$

Step 1.1.2.30.4.4.4

Combine the numerators over the common denominator.

$\frac{27 x^{3} + 2 x}{{(9 x^{2} + 1)}^{\frac{2 + 1}{2}} x^{4}}$

Step 1.1.2.30.4.4.5

Add $2$ and $1$ .

$\frac{27 x^{3} + 2 x}{{(9 x^{2} + 1)}^{\frac{3}{2}} x^{4}}$

Step 1.1.2.30.5

Reorder terms.

$\frac{27 x^{3} + 2 x}{x^{4} {(9 x^{2} + 1)}^{\frac{3}{2}}}$

Step 1.1.2.30.6

Factor $x$ out of $27 x^{3} + 2 x$ .

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Step 1.1.2.30.6.1

Factor $x$ out of $27 x^{3}$ .

$\frac{x (27 x^{2}) + 2 x}{x^{4} {(9 x^{2} + 1)}^{\frac{3}{2}}}$

Step 1.1.2.30.6.2

Factor $x$ out of $2 x$ .

$\frac{x (27 x^{2}) + x \cdot 2}{x^{4} {(9 x^{2} + 1)}^{\frac{3}{2}}}$

Step 1.1.2.30.6.3

Factor $x$ out of $x (27 x^{2}) + x \cdot 2$ .

$\frac{x (27 x^{2} + 2)}{x^{4} {(9 x^{2} + 1)}^{\frac{3}{2}}}$

Step 1.1.2.30.7

Cancel the common factors.

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Step 1.1.2.30.7.1

Factor $x$ out of $x^{4} {(9 x^{2} + 1)}^{\frac{3}{2}}$ .

$\frac{x (27 x^{2} + 2)}{x (x^{3} {(9 x^{2} + 1)}^{\frac{3}{2}})}$

Step 1.1.2.30.7.2

Cancel the common factor.

$\frac{x (27 x^{2} + 2)}{x (x^{3} {(9 x^{2} + 1)}^{\frac{3}{2}})}$

Step 1.1.2.30.7.3

Rewrite the expression.

$f'' (x) = \frac{27 x^{2} + 2}{x^{3} {(9 x^{2} + 1)}^{\frac{3}{2}}}$

Step 1.1.3

The second derivative of $f (x)$ with respect to $x$ is $\frac{27 x^{2} + 2}{x^{3} {(9 x^{2} + 1)}^{\frac{3}{2}}}$ .

$\frac{27 x^{2} + 2}{x^{3} {(9 x^{2} + 1)}^{\frac{3}{2}}}$

Step 1.2

Set the second derivative equal to $0$ then solve the equation $\frac{27 x^{2} + 2}{x^{3} {(9 x^{2} + 1)}^{\frac{3}{2}}} = 0$ .

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Step 1.2.1

Set the second derivative equal to $0$ .

$\frac{27 x^{2} + 2}{x^{3} {(9 x^{2} + 1)}^{\frac{3}{2}}} = 0$

Step 1.2.2

Set the numerator equal to zero.

$27 x^{2} + 2 = 0$

Step 1.2.3

Solve the equation for $x$ .

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Step 1.2.3.1

Subtract $2$ from both sides of the equation.

$27 x^{2} = - 2$

Step 1.2.3.2

Divide each term in $27 x^{2} = - 2$ by $27$ and simplify.

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Step 1.2.3.2.1

Divide each term in $27 x^{2} = - 2$ by $27$ .

$\frac{27 x^{2}}{27} = \frac{- 2}{27}$

Step 1.2.3.2.2

Simplify the left side.

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Step 1.2.3.2.2.1

Cancel the common factor of $27$ .

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Step 1.2.3.2.2.1.1

Cancel the common factor.

$\frac{27 x^{2}}{27} = \frac{- 2}{27}$

Step 1.2.3.2.2.1.2

Divide $x^{2}$ by $1$ .

$x^{2} = \frac{- 2}{27}$

Step 1.2.3.2.3

Simplify the right side.

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Step 1.2.3.2.3.1

Move the negative in front of the fraction.

$x^{2} = - \frac{2}{27}$

Step 1.2.3.3

Take the specified root of both sides of the equation to eliminate the exponent on the left side.

$x = \pm \sqrt{- \frac{2}{27}}$

Step 1.2.3.4

Simplify $\pm \sqrt{- \frac{2}{27}}$ .

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Step 1.2.3.4.1

Rewrite $- \frac{2}{27}$ as ${(\frac{i}{3})}^{2} \frac{2}{3}$ .

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Step 1.2.3.4.1.1

Rewrite $- 1$ as $i^{2}$ .

$x = \pm \sqrt{i^{2} \frac{2}{27}}$

Step 1.2.3.4.1.2

Factor the perfect power $1^{2}$ out of $2$ .

$x = \pm \sqrt{i^{2} \frac{1^{2} \cdot 2}{27}}$

Step 1.2.3.4.1.3

Factor the perfect power $3^{2}$ out of $27$ .

$x = \pm \sqrt{i^{2} \frac{1^{2} \cdot 2}{3^{2} \cdot 3}}$

Step 1.2.3.4.1.4

Rearrange the fraction $\frac{1^{2} \cdot 2}{3^{2} \cdot 3}$ .

$x = \pm \sqrt{i^{2} ({(\frac{1}{3})}^{2} \frac{2}{3})}$

Step 1.2.3.4.1.5

Rewrite $i^{2} {(\frac{1}{3})}^{2}$ as ${(\frac{i}{3})}^{2}$ .

$x = \pm \sqrt{{(\frac{i}{3})}^{2} \frac{2}{3}}$

Step 1.2.3.4.2

Pull terms out from under the radical.

$x = \pm \frac{i}{3} \sqrt{\frac{2}{3}}$

Step 1.2.3.4.3

Rewrite $\sqrt{\frac{2}{3}}$ as $\frac{\sqrt{2}}{\sqrt{3}}$ .

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2}}{\sqrt{3}}$

Step 1.2.3.4.4

Multiply $\frac{\sqrt{2}}{\sqrt{3}}$ by $\frac{\sqrt{3}}{\sqrt{3}}$ .

$x = \pm \frac{i}{3} (\frac{\sqrt{2}}{\sqrt{3}} \cdot \frac{\sqrt{3}}{\sqrt{3}})$

Step 1.2.3.4.5

Combine and simplify the denominator.

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Step 1.2.3.4.5.1

Multiply $\frac{\sqrt{2}}{\sqrt{3}}$ by $\frac{\sqrt{3}}{\sqrt{3}}$ .

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2} \sqrt{3}}{\sqrt{3} \sqrt{3}}$

Step 1.2.3.4.5.2

Raise $\sqrt{3}$ to the power of $1$ .

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2} \sqrt{3}}{{\sqrt{3}}^{1} \sqrt{3}}$

Step 1.2.3.4.5.3

Raise $\sqrt{3}$ to the power of $1$ .

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2} \sqrt{3}}{{\sqrt{3}}^{1} {\sqrt{3}}^{1}}$

Step 1.2.3.4.5.4

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2} \sqrt{3}}{{\sqrt{3}}^{1 + 1}}$

Step 1.2.3.4.5.5

Add $1$ and $1$ .

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2} \sqrt{3}}{{\sqrt{3}}^{2}}$

Step 1.2.3.4.5.6

Rewrite ${\sqrt{3}}^{2}$ as $3$ .

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Step 1.2.3.4.5.6.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{3}$ as $3^{\frac{1}{2}}$ .

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2} \sqrt{3}}{{(3^{\frac{1}{2}})}^{2}}$

Step 1.2.3.4.5.6.2

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2} \sqrt{3}}{3^{\frac{1}{2} \cdot 2}}$

Step 1.2.3.4.5.6.3

Combine $\frac{1}{2}$ and $2$ .

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2} \sqrt{3}}{3^{\frac{2}{2}}}$

Step 1.2.3.4.5.6.4

Cancel the common factor of $2$ .

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Step 1.2.3.4.5.6.4.1

Cancel the common factor.

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2} \sqrt{3}}{3^{\frac{2}{2}}}$

Step 1.2.3.4.5.6.4.2

Rewrite the expression.

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2} \sqrt{3}}{3^{1}}$

Step 1.2.3.4.5.6.5

Evaluate the exponent.

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2} \sqrt{3}}{3}$

Step 1.2.3.4.6

Simplify the numerator.

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Step 1.2.3.4.6.1

Combine using the product rule for radicals.

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{2 \cdot 3}}{3}$

Step 1.2.3.4.6.2

Multiply $2$ by $3$ .

$x = \pm \frac{i}{3} \cdot \frac{\sqrt{6}}{3}$

Step 1.2.3.4.7

Multiply $\frac{i}{3} \cdot \frac{\sqrt{6}}{3}$ .

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Step 1.2.3.4.7.1

Multiply $\frac{i}{3}$ by $\frac{\sqrt{6}}{3}$ .

$x = \pm \frac{i \sqrt{6}}{3 \cdot 3}$

Step 1.2.3.4.7.2

Multiply $3$ by $3$ .

$x = \pm \frac{i \sqrt{6}}{9}$

Step 1.2.3.5

The complete solution is the result of both the positive and negative portions of the solution.

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Step 1.2.3.5.1

First, use the positive value of the $\pm$ to find the first solution.

$x = \frac{i \sqrt{6}}{9}$

Step 1.2.3.5.2

Next, use the negative value of the $\pm$ to find the second solution.

$x = - \frac{i \sqrt{6}}{9}$

Step 1.2.3.5.3

The complete solution is the result of both the positive and negative portions of the solution.

$x = \frac{i \sqrt{6}}{9}, - \frac{i \sqrt{6}}{9}$

Step 2

Find the domain of $f (x) = \frac{\sqrt{9 x^{2} + 1}}{x}$ .

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Step 2.1

Set the radicand in $\sqrt{9 x^{2} + 1}$ greater than or equal to $0$ to find where the expression is defined.

$9 x^{2} + 1 \geq 0$

Step 2.2

Solve for $x$ .

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Step 2.2.1

Subtract $1$ from both sides of the inequality.

$9 x^{2} \geq - 1$

Step 2.2.2

Divide each term in $9 x^{2} \geq - 1$ by $9$ and simplify.

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Step 2.2.2.1

Divide each term in $9 x^{2} \geq - 1$ by $9$ .

$\frac{9 x^{2}}{9} \geq \frac{- 1}{9}$

Step 2.2.2.2

Simplify the left side.

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Step 2.2.2.2.1

Cancel the common factor of $9$ .

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Step 2.2.2.2.1.1

Cancel the common factor.

$\frac{9 x^{2}}{9} \geq \frac{- 1}{9}$

Step 2.2.2.2.1.2

Divide $x^{2}$ by $1$ .

$x^{2} \geq \frac{- 1}{9}$

Step 2.2.2.3

Simplify the right side.

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Step 2.2.2.3.1

Move the negative in front of the fraction.

$x^{2} \geq - \frac{1}{9}$

Step 2.2.3

Since the left side has an even power, it is always positive for all real numbers.

All real numbers

Step 2.3

Set the denominator in $\frac{\sqrt{9 x^{2} + 1}}{x}$ equal to $0$ to find where the expression is undefined.

$x = 0$

Step 2.4

The domain is all values of $x$ that make the expression defined.

Interval Notation:

$(- \infty, 0) \cup (0, \infty)$

Set-Builder Notation:

${x | x \neq 0}$

Interval Notation:

$(- \infty, 0) \cup (0, \infty)$

Set-Builder Notation:

${x | x \neq 0}$

Step 3

Create intervals around the $x$ -values where the second derivative is zero or undefined.

$(- \infty, 0) \cup (0, \infty)$

Step 4

Substitute any number from the interval $(- \infty, 0)$ into the second derivative and evaluate to determine the concavity.

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Step 4.1

Replace the variable $x$ with $- 2$ in the expression.

$f'' (- 2) = \frac{27 {(- 2)}^{2} + 2}{{(- 2)}^{3} {(9 {(- 2)}^{2} + 1)}^{\frac{3}{2}}}$

Step 4.2

Simplify the result.

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Step 4.2.1

Simplify the numerator.

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Step 4.2.1.1

Raise $- 2$ to the power of $2$ .

$f'' (- 2) = \frac{27 \cdot 4 + 2}{{(- 2)}^{3} {(9 {(- 2)}^{2} + 1)}^{\frac{3}{2}}}$

Step 4.2.1.2

Multiply $27$ by $4$ .

$f'' (- 2) = \frac{108 + 2}{{(- 2)}^{3} {(9 {(- 2)}^{2} + 1)}^{\frac{3}{2}}}$

Step 4.2.1.3

Add $108$ and $2$ .

$f'' (- 2) = \frac{110}{{(- 2)}^{3} {(9 {(- 2)}^{2} + 1)}^{\frac{3}{2}}}$

Step 4.2.2

Simplify the denominator.

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Step 4.2.2.1

Raise $- 2$ to the power of $3$ .

$f'' (- 2) = \frac{110}{- 8 {(9 {(- 2)}^{2} + 1)}^{\frac{3}{2}}}$

Step 4.2.2.2

Simplify each term.

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Step 4.2.2.2.1

Raise $- 2$ to the power of $2$ .

$f'' (- 2) = \frac{110}{- 8 {(9 \cdot 4 + 1)}^{\frac{3}{2}}}$

Step 4.2.2.2.2

Multiply $9$ by $4$ .

$f'' (- 2) = \frac{110}{- 8 {(36 + 1)}^{\frac{3}{2}}}$

Step 4.2.2.3

Add $36$ and $1$ .

$f'' (- 2) = \frac{110}{- 8 \cdot 37^{\frac{3}{2}}}$

Step 4.2.3

Factor $2$ out of $110$ .

$f'' (- 2) = \frac{2 (55)}{- 8 \cdot 37^{\frac{3}{2}}}$

Step 4.2.4

Cancel the common factors.

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Step 4.2.4.1

Factor $2$ out of $- 8 \cdot 37^{\frac{3}{2}}$ .

$f'' (- 2) = \frac{2 (55)}{2 (- 4 \cdot 37^{\frac{3}{2}})}$

Step 4.2.4.2

Cancel the common factor.

$f'' (- 2) = \frac{2 \cdot 55}{2 (- 4 \cdot 37^{\frac{3}{2}})}$

Step 4.2.4.3

Rewrite the expression.

$f'' (- 2) = \frac{55}{- 4 \cdot 37^{\frac{3}{2}}}$

Step 4.2.5

Move the negative in front of the fraction.

$f'' (- 2) = - \frac{55}{4 \cdot 37^{\frac{3}{2}}}$

Step 4.2.6

The final answer is $- \frac{55}{4 \cdot 37^{\frac{3}{2}}}$ .

$- \frac{55}{4 \cdot 37^{\frac{3}{2}}}$

Step 4.3

The graph is concave down on the interval $(- \infty, 0)$ because $f'' (- 2)$ is negative.

Concave down on $(- \infty, 0)$ since $f'' (x)$ is negative

Step 5

Substitute any number from the interval $(0, \infty)$ into the second derivative and evaluate to determine the concavity.

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Step 5.1

Replace the variable $x$ with $2$ in the expression.

$f'' (2) = \frac{27 {(2)}^{2} + 2}{{(2)}^{3} {(9 {(2)}^{2} + 1)}^{\frac{3}{2}}}$

Step 5.2

Simplify the result.

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Step 5.2.1

Simplify the numerator.

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Step 5.2.1.1

Raise $2$ to the power of $2$ .

$f'' (2) = \frac{27 \cdot 4 + 2}{2^{3} {(9 \cdot 2^{2} + 1)}^{\frac{3}{2}}}$

Step 5.2.1.2

Multiply $27$ by $4$ .

$f'' (2) = \frac{108 + 2}{2^{3} {(9 \cdot 2^{2} + 1)}^{\frac{3}{2}}}$

Step 5.2.1.3

Add $108$ and $2$ .

$f'' (2) = \frac{110}{2^{3} {(9 \cdot 2^{2} + 1)}^{\frac{3}{2}}}$

Step 5.2.2

Simplify the denominator.

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Step 5.2.2.1

Raise $2$ to the power of $3$ .

$f'' (2) = \frac{110}{8 {(9 \cdot 2^{2} + 1)}^{\frac{3}{2}}}$

Step 5.2.2.2

Simplify each term.

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Step 5.2.2.2.1

Raise $2$ to the power of $2$ .

$f'' (2) = \frac{110}{8 {(9 \cdot 4 + 1)}^{\frac{3}{2}}}$

Step 5.2.2.2.2

Multiply $9$ by $4$ .

$f'' (2) = \frac{110}{8 {(36 + 1)}^{\frac{3}{2}}}$

Step 5.2.2.3

Add $36$ and $1$ .

$f'' (2) = \frac{110}{8 \cdot 37^{\frac{3}{2}}}$

Step 5.2.3

Factor $2$ out of $110$ .

$f'' (2) = \frac{2 (55)}{8 \cdot 37^{\frac{3}{2}}}$

Step 5.2.4

Cancel the common factors.

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Step 5.2.4.1

Factor $2$ out of $8 \cdot 37^{\frac{3}{2}}$ .

$f'' (2) = \frac{2 (55)}{2 (4 \cdot 37^{\frac{3}{2}})}$

Step 5.2.4.2

Cancel the common factor.

$f'' (2) = \frac{2 \cdot 55}{2 (4 \cdot 37^{\frac{3}{2}})}$

Step 5.2.4.3

Rewrite the expression.

$f'' (2) = \frac{55}{4 \cdot 37^{\frac{3}{2}}}$

Step 5.2.5

The final answer is $\frac{55}{4 \cdot 37^{\frac{3}{2}}}$ .

$\frac{55}{4 \cdot 37^{\frac{3}{2}}}$

Step 5.3

The graph is concave up on the interval $(0, \infty)$ because $f'' (2)$ is positive.

Concave up on $(0, \infty)$ since $f'' (x)$ is positive

Step 6

The graph is concave down when the second derivative is negative and concave up when the second derivative is positive.

Concave down on $(- \infty, 0)$ since $f'' (x)$ is negative

Concave up on $(0, \infty)$ since $f'' (x)$ is positive

Step 7