Calculus Examples

$x \cdot \sqrt{8 x - x^{2}}$

Step 1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{8 x - x^{2}}$ as ${(8 x - x^{2})}^{\frac{1}{2}}$ .

$\frac{d}{d x} [x {(8 x - x^{2})}^{\frac{1}{2}}]$

Step 2

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 $f (x) = x$ and $g (x) = {(8 x - x^{2})}^{\frac{1}{2}}$ .

$x \frac{d}{d x} [{(8 x - x^{2})}^{\frac{1}{2}}] + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 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 $g (x) = 8 x - x^{2}$ .

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Step 3.1

To apply the Chain Rule, set $u$ as $8 x - x^{2}$ .

$x (\frac{d}{d u} [u^{\frac{1}{2}}] \frac{d}{d x} [8 x - x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 3.2

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

$x (\frac{1}{2} u^{\frac{1}{2} - 1} \frac{d}{d x} [8 x - x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 3.3

Replace all occurrences of $u$ with $8 x - x^{2}$ .

$x (\frac{1}{2} {(8 x - x^{2})}^{\frac{1}{2} - 1} \frac{d}{d x} [8 x - x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 4

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

$x (\frac{1}{2} {(8 x - x^{2})}^{\frac{1}{2} - 1 \cdot \frac{2}{2}} \frac{d}{d x} [8 x - x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 5

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

$x (\frac{1}{2} {(8 x - x^{2})}^{\frac{1}{2} + \frac{- 1 \cdot 2}{2}} \frac{d}{d x} [8 x - x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 6

Combine the numerators over the common denominator.

$x (\frac{1}{2} {(8 x - x^{2})}^{\frac{1 - 1 \cdot 2}{2}} \frac{d}{d x} [8 x - x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 7

Simplify the numerator.

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Step 7.1

Multiply $- 1$ by $2$ .

$x (\frac{1}{2} {(8 x - x^{2})}^{\frac{1 - 2}{2}} \frac{d}{d x} [8 x - x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 7.2

Subtract $2$ from $1$ .

$x (\frac{1}{2} {(8 x - x^{2})}^{\frac{- 1}{2}} \frac{d}{d x} [8 x - x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 8

Combine fractions.

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Step 8.1

Move the negative in front of the fraction.

$x (\frac{1}{2} {(8 x - x^{2})}^{- \frac{1}{2}} \frac{d}{d x} [8 x - x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 8.2

Combine $\frac{1}{2}$ and ${(8 x - x^{2})}^{- \frac{1}{2}}$ .

$x (\frac{{(8 x - x^{2})}^{- \frac{1}{2}}}{2} \frac{d}{d x} [8 x - x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 8.3

Move ${(8 x - x^{2})}^{- \frac{1}{2}}$ to the denominator using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$x (\frac{1}{2 {(8 x - x^{2})}^{\frac{1}{2}}} \frac{d}{d x} [8 x - x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 8.4

Combine $\frac{1}{2 {(8 x - x^{2})}^{\frac{1}{2}}}$ and $x$ .

$\frac{x}{2 {(8 x - x^{2})}^{\frac{1}{2}}} \frac{d}{d x} [8 x - x^{2}] + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 9

By the Sum Rule, the derivative of $8 x - x^{2}$ with respect to $x$ is $\frac{d}{d x} [8 x] + \frac{d}{d x} [- x^{2}]$ .

$\frac{x}{2 {(8 x - x^{2})}^{\frac{1}{2}}} (\frac{d}{d x} [8 x] + \frac{d}{d x} [- x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 10

Since $8$ is constant with respect to $x$ , the derivative of $8 x$ with respect to $x$ is $8 \frac{d}{d x} [x]$ .

$\frac{x}{2 {(8 x - x^{2})}^{\frac{1}{2}}} (8 \frac{d}{d x} [x] + \frac{d}{d x} [- x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 11

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

$\frac{x}{2 {(8 x - x^{2})}^{\frac{1}{2}}} (8 \cdot 1 + \frac{d}{d x} [- x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 12

Multiply $8$ by $1$ .

$\frac{x}{2 {(8 x - x^{2})}^{\frac{1}{2}}} (8 + \frac{d}{d x} [- x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 13

Since $- 1$ is constant with respect to $x$ , the derivative of $- x^{2}$ with respect to $x$ is $- \frac{d}{d x} [x^{2}]$ .

$\frac{x}{2 {(8 x - x^{2})}^{\frac{1}{2}}} (8 - \frac{d}{d x} [x^{2}]) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 14

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

$\frac{x}{2 {(8 x - x^{2})}^{\frac{1}{2}}} (8 - (2 x)) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 15

Multiply $2$ by $- 1$ .

$\frac{x}{2 {(8 x - x^{2})}^{\frac{1}{2}}} (8 - 2 x) + {(8 x - x^{2})}^{\frac{1}{2}} \frac{d}{d x} [x]$

Step 16

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

$\frac{x}{2 {(8 x - x^{2})}^{\frac{1}{2}}} (8 - 2 x) + {(8 x - x^{2})}^{\frac{1}{2}} \cdot 1$

Step 17

Multiply ${(8 x - x^{2})}^{\frac{1}{2}}$ by $1$ .

$\frac{x}{2 {(8 x - x^{2})}^{\frac{1}{2}}} (8 - 2 x) + {(8 x - x^{2})}^{\frac{1}{2}}$

Step 18

Simplify.

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Step 18.1

Reorder terms.

$(8 - 2 x) \frac{x}{2 {(8 x - x^{2})}^{\frac{1}{2}}} + {(8 x - x^{2})}^{\frac{1}{2}}$

Step 18.2

Simplify each term.

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Step 18.2.1

Multiply $8 - 2 x$ by $\frac{x}{2 {(8 x - x^{2})}^{\frac{1}{2}}}$ .

$\frac{(8 - 2 x) x}{2 {(8 x - x^{2})}^{\frac{1}{2}}} + {(8 x - x^{2})}^{\frac{1}{2}}$

Step 18.2.2

Factor $2$ out of $(8 - 2 x) x$ .

$\frac{2 ((4 - x) x)}{2 {(8 x - x^{2})}^{\frac{1}{2}}} + {(8 x - x^{2})}^{\frac{1}{2}}$

Step 18.2.3

Cancel the common factors.

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Step 18.2.3.1

Factor $2$ out of $2 {(8 x - x^{2})}^{\frac{1}{2}}$ .

$\frac{2 ((4 - x) x)}{2 ({(8 x - x^{2})}^{\frac{1}{2}})} + {(8 x - x^{2})}^{\frac{1}{2}}$

Step 18.2.3.2

Cancel the common factor.

$\frac{2 ((4 - x) x)}{2 {(8 x - x^{2})}^{\frac{1}{2}}} + {(8 x - x^{2})}^{\frac{1}{2}}$

Step 18.2.3.3

Rewrite the expression.

$\frac{(4 - x) x}{{(8 x - x^{2})}^{\frac{1}{2}}} + {(8 x - x^{2})}^{\frac{1}{2}}$

Step 18.3

To write ${(8 x - x^{2})}^{\frac{1}{2}}$ as a fraction with a common denominator, multiply by $\frac{{(8 x - x^{2})}^{\frac{1}{2}}}{{(8 x - x^{2})}^{\frac{1}{2}}}$ .

$\frac{(4 - x) x}{{(8 x - x^{2})}^{\frac{1}{2}}} + \frac{{(8 x - x^{2})}^{\frac{1}{2}} {(8 x - x^{2})}^{\frac{1}{2}}}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.4

Combine the numerators over the common denominator.

$\frac{(4 - x) x + {(8 x - x^{2})}^{\frac{1}{2}} {(8 x - x^{2})}^{\frac{1}{2}}}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5

Simplify the numerator.

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Step 18.5.1

Apply the distributive property.

$\frac{4 x - x \cdot x + {(8 x - x^{2})}^{\frac{1}{2}} {(8 x - x^{2})}^{\frac{1}{2}}}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5.2

Multiply $x$ by $x$ by adding the exponents.

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Step 18.5.2.1

Move $x$ .

$\frac{4 x - (x \cdot x) + {(8 x - x^{2})}^{\frac{1}{2}} {(8 x - x^{2})}^{\frac{1}{2}}}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5.2.2

Multiply $x$ by $x$ .

$\frac{4 x - x^{2} + {(8 x - x^{2})}^{\frac{1}{2}} {(8 x - x^{2})}^{\frac{1}{2}}}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5.3

Multiply ${(8 x - x^{2})}^{\frac{1}{2}}$ by ${(8 x - x^{2})}^{\frac{1}{2}}$ by adding the exponents.

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Step 18.5.3.1

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

$\frac{4 x - x^{2} + {(8 x - x^{2})}^{\frac{1}{2} + \frac{1}{2}}}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5.3.2

Combine the numerators over the common denominator.

$\frac{4 x - x^{2} + {(8 x - x^{2})}^{\frac{1 + 1}{2}}}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5.3.3

Add $1$ and $1$ .

$\frac{4 x - x^{2} + {(8 x - x^{2})}^{\frac{2}{2}}}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5.3.4

Divide $2$ by $2$ .

$\frac{4 x - x^{2} + {(8 x - x^{2})}^{1}}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5.4

Simplify ${(8 x - x^{2})}^{1}$ .

$\frac{4 x - x^{2} + 8 x - x^{2}}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5.5

Add $4 x$ and $8 x$ .

$\frac{- x^{2} + 12 x - x^{2}}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5.6

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

$\frac{- 2 x^{2} + 12 x}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5.7

Factor $2 x$ out of $- 2 x^{2} + 12 x$ .

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Step 18.5.7.1

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

$\frac{2 x (- x) + 12 x}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5.7.2

Factor $2 x$ out of $12 x$ .

$\frac{2 x (- x) + 2 x (6)}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.5.7.3

Factor $2 x$ out of $2 x (- x) + 2 x (6)$ .

$\frac{2 x (- x + 6)}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.6

Factor $- 1$ out of $- x$ .

$\frac{2 x (- (x) + 6)}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.7

Rewrite $6$ as $- 1 (- 6)$ .

$\frac{2 x (- (x) - 1 (- 6))}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.8

Factor $- 1$ out of $- (x) - 1 (- 6)$ .

$\frac{2 x (- (x - 6))}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.9

Rewrite $- (x - 6)$ as $- 1 (x - 6)$ .

$\frac{2 x (- 1 (x - 6))}{{(8 x - x^{2})}^{\frac{1}{2}}}$

Step 18.10

Move the negative in front of the fraction.

$- \frac{(2 x) (x - 6)}{{(8 x - x^{2})}^{\frac{1}{2}}}$