Calculus Examples

$\frac{8}{x^{2} + 4}$

Step 1

Differentiate using the Constant Multiple Rule.

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Step 1.1

Since $8$ is constant with respect to $x$ , the derivative of $\frac{8}{x^{2} + 4}$ with respect to $x$ is $8 \frac{d}{d x} [\frac{1}{x^{2} + 4}]$ .

$8 \frac{d}{d x} [\frac{1}{x^{2} + 4}]$

Step 1.2

Rewrite $\frac{1}{x^{2} + 4}$ as ${(x^{2} + 4)}^{- 1}$ .

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

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 $g (x) = x^{2} + 4$ .

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Step 2.1

To apply the Chain Rule, set $u$ as $x^{2} + 4$ .

$8 (\frac{d}{d u} [u^{- 1}] \frac{d}{d x} [x^{2} + 4])$

Step 2.2

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

$8 (- u^{- 2} \frac{d}{d x} [x^{2} + 4])$

Step 2.3

Replace all occurrences of $u$ with $x^{2} + 4$ .

$8 (- {(x^{2} + 4)}^{- 2} \frac{d}{d x} [x^{2} + 4])$

Step 3

Differentiate.

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Step 3.1

Multiply $- 1$ by $8$ .

$- 8 ({(x^{2} + 4)}^{- 2} \frac{d}{d x} [x^{2} + 4])$

Step 3.2

By the Sum Rule, the derivative of $x^{2} + 4$ with respect to $x$ is $\frac{d}{d x} [x^{2}] + \frac{d}{d x} [4]$ .

$- 8 {(x^{2} + 4)}^{- 2} (\frac{d}{d x} [x^{2}] + \frac{d}{d x} [4])$

Step 3.3

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

$- 8 {(x^{2} + 4)}^{- 2} (2 x + \frac{d}{d x} [4])$

Step 3.4

Since $4$ is constant with respect to $x$ , the derivative of $4$ with respect to $x$ is $0$ .

$- 8 {(x^{2} + 4)}^{- 2} (2 x + 0)$

Step 3.5

Simplify the expression.

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Step 3.5.1

Add $2 x$ and $0$ .

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

Step 3.5.2

Multiply $2$ by $- 8$ .

$- 16 {(x^{2} + 4)}^{- 2} x$

Step 4

Simplify.

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Step 4.1

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

$- 16 \frac{1}{{(x^{2} + 4)}^{2}} x$

Step 4.2

Combine terms.

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Step 4.2.1

Combine $- 16$ and $\frac{1}{{(x^{2} + 4)}^{2}}$ .

$\frac{- 16}{{(x^{2} + 4)}^{2}} x$

Step 4.2.2

Move the negative in front of the fraction.

$- \frac{16}{{(x^{2} + 4)}^{2}} x$

Step 4.2.3

Combine $x$ and $\frac{16}{{(x^{2} + 4)}^{2}}$ .

$- \frac{x \cdot 16}{{(x^{2} + 4)}^{2}}$

Step 4.2.4

Move $16$ to the left of $x$ .

$- \frac{16 x}{{(x^{2} + 4)}^{2}}$