Calculus Examples

$\frac{4}{1 + x^{2}}$

Step 1

Differentiate using the Constant Multiple Rule.

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Step 1.1

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

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

Step 1.2

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

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

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 $g (x) = 1 + x^{2}$ .

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Step 2.1

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

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

Step 2.2

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

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

Step 2.3

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

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

Step 3

Differentiate.

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Step 3.1

Multiply $- 1$ by $4$ .

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

Step 3.2

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

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

Step 3.3

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

$- 4 {(1 + x^{2})}^{- 2} (0 + \frac{d}{d x} [x^{2}])$

Step 3.4

Add $0$ and $\frac{d}{d x} [x^{2}]$ .

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

Step 3.5

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

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

Step 3.6

Multiply $2$ by $- 4$ .

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

Step 4

Simplify.

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Step 4.1

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

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

Step 4.2

Combine terms.

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Step 4.2.1

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

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

Step 4.2.2

Move the negative in front of the fraction.

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

Step 4.2.3

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

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

Step 4.2.4

Move $8$ to the left of $x$ .

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