Calculus Examples

$90 + \frac{4}{x + 1}$

Step 1

Differentiate.

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Step 1.1

By the Sum Rule, the derivative of $90 + \frac{4}{x + 1}$ with respect to $x$ is $\frac{d}{d x} [90] + \frac{d}{d x} [\frac{4}{x + 1}]$ .

$\frac{d}{d x} [90] + \frac{d}{d x} [\frac{4}{x + 1}]$

Step 1.2

Since $90$ is constant with respect to $x$ , the derivative of $90$ with respect to $x$ is $0$ .

$0 + \frac{d}{d x} [\frac{4}{x + 1}]$

Step 2

Evaluate $\frac{d}{d x} [\frac{4}{x + 1}]$ .

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Step 2.1

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

$0 + 4 \frac{d}{d x} [\frac{1}{x + 1}]$

Step 2.2

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

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

Step 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 $g (x) = x + 1$ .

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Step 2.3.1

To apply the Chain Rule, set $u$ as $x + 1$ .

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

Step 2.3.2

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

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

Step 2.3.3

Replace all occurrences of $u$ with $x + 1$ .

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

Step 2.4

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

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

Step 2.5

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

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

Step 2.6

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

$0 + 4 (- {(x + 1)}^{- 2} (1 + 0))$

Step 2.7

Add $1$ and $0$ .

$0 + 4 (- {(x + 1)}^{- 2} \cdot 1)$

Step 2.8

Multiply $- 1$ by $1$ .

$0 + 4 (- {(x + 1)}^{- 2})$

Step 2.9

Multiply $- 1$ by $4$ .

$0 - 4 {(x + 1)}^{- 2}$

Step 3

Simplify.

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Step 3.1

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

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

Step 3.2

Combine terms.

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Step 3.2.1

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

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

Step 3.2.2

Move the negative in front of the fraction.

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

Step 3.2.3

Subtract $\frac{4}{{(x + 1)}^{2}}$ from $0$ .

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