Calculus Examples

$f (x) = \frac{9}{x^{2} + 5}$

Step 1

Differentiate using the Constant Multiple Rule.

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Step 1.1

Since $9$ is constant with respect to $x$ , the derivative of $\frac{9}{x^{2} + 5}$ with respect to $x$ is $9 \frac{d}{d x} [\frac{1}{x^{2} + 5}]$ .

$9 \frac{d}{d x} [\frac{1}{x^{2} + 5}]$

Step 1.2

Rewrite $\frac{1}{x^{2} + 5}$ as ${(x^{2} + 5)}^{- 1}$ .

$9 \frac{d}{d x} [{(x^{2} + 5)}^{- 1}]$

Step 2

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 $g (x) = x^{2} + 5$ .

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Step 2.1

To apply the Chain Rule, set $u$ as $x^{2} + 5$ .

$9 (\frac{d}{d u} [u^{- 1}] \frac{d}{d x} [x^{2} + 5])$

Step 2.2

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

$9 (- u^{- 2} \frac{d}{d x} [x^{2} + 5])$

Step 2.3

Replace all occurrences of $u$ with $x^{2} + 5$ .

$9 (- {(x^{2} + 5)}^{- 2} \frac{d}{d x} [x^{2} + 5])$

Step 3

Differentiate.

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Step 3.1

Multiply $- 1$ by $9$ .

$- 9 ({(x^{2} + 5)}^{- 2} \frac{d}{d x} [x^{2} + 5])$

Step 3.2

By the Sum Rule, the derivative of $x^{2} + 5$ with respect to $x$ is $\frac{d}{d x} [x^{2}] + \frac{d}{d x} [5]$ .

$- 9 {(x^{2} + 5)}^{- 2} (\frac{d}{d x} [x^{2}] + \frac{d}{d x} [5])$

Step 3.3

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

$- 9 {(x^{2} + 5)}^{- 2} (2 x + \frac{d}{d x} [5])$

Step 3.4

Since $5$ is constant with respect to $x$ , the derivative of $5$ with respect to $x$ is $0$ .

$- 9 {(x^{2} + 5)}^{- 2} (2 x + 0)$

Step 3.5

Simplify the expression.

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Step 3.5.1

Add $2 x$ and $0$ .

$- 9 {(x^{2} + 5)}^{- 2} (2 x)$

Step 3.5.2

Multiply $2$ by $- 9$ .

$- 18 {(x^{2} + 5)}^{- 2} x$

Step 4

Simplify.

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Step 4.1

Rewrite the expression using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$- 18 \frac{1}{{(x^{2} + 5)}^{2}} x$

Step 4.2

Combine terms.

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Step 4.2.1

Combine $- 18$ and $\frac{1}{{(x^{2} + 5)}^{2}}$ .

$\frac{- 18}{{(x^{2} + 5)}^{2}} x$

Step 4.2.2

Move the negative in front of the fraction.

$- \frac{18}{{(x^{2} + 5)}^{2}} x$

Step 4.2.3

Combine $x$ and $\frac{18}{{(x^{2} + 5)}^{2}}$ .

$- \frac{x \cdot 18}{{(x^{2} + 5)}^{2}}$

Step 4.2.4

Move $18$ to the left of $x$ .

$- \frac{18 x}{{(x^{2} + 5)}^{2}}$