Calculus Examples

$\ln (\frac{3 x + 1}{3 x - 1})$

Step 1

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \ln (x)$ and $g (x) = \frac{3 x + 1}{3 x - 1}$ .

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Step 1.1

To apply the Chain Rule, set $u$ as $\frac{3 x + 1}{3 x - 1}$ .

$\frac{d}{d u} [\ln (u)] \frac{d}{d x} [\frac{3 x + 1}{3 x - 1}]$

Step 1.2

The derivative of $\ln (u)$ with respect to $u$ is $\frac{1}{u}$ .

$\frac{1}{u} \frac{d}{d x} [\frac{3 x + 1}{3 x - 1}]$

Step 1.3

Replace all occurrences of $u$ with $\frac{3 x + 1}{3 x - 1}$ .

$\frac{1}{\frac{3 x + 1}{3 x - 1}} \frac{d}{d x} [\frac{3 x + 1}{3 x - 1}]$

Step 2

Multiply by the reciprocal of the fraction to divide by $\frac{3 x + 1}{3 x - 1}$ .

$1 \frac{3 x - 1}{3 x + 1} \frac{d}{d x} [\frac{3 x + 1}{3 x - 1}]$

Step 3

Multiply $\frac{3 x - 1}{3 x + 1}$ by $1$ .

$\frac{3 x - 1}{3 x + 1} \frac{d}{d x} [\frac{3 x + 1}{3 x - 1}]$

Step 4

Differentiate using the Quotient Rule which states that $\frac{d}{d x} [\frac{f (x)}{g (x)}]$ is $\frac{g (x) \frac{d}{d x} [f (x)] - f (x) \frac{d}{d x} [g (x)]}{{g (x)}^{2}}$ where $f (x) = 3 x + 1$ and $g (x) = 3 x - 1$ .

$\frac{3 x - 1}{3 x + 1} \cdot \frac{(3 x - 1) \frac{d}{d x} [3 x + 1] - (3 x + 1) \frac{d}{d x} [3 x - 1]}{{(3 x - 1)}^{2}}$

Step 5

Differentiate.

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Step 5.1

By the Sum Rule, the derivative of $3 x + 1$ with respect to $x$ is $\frac{d}{d x} [3 x] + \frac{d}{d x} [1]$ .

$\frac{3 x - 1}{3 x + 1} \cdot \frac{(3 x - 1) (\frac{d}{d x} [3 x] + \frac{d}{d x} [1]) - (3 x + 1) \frac{d}{d x} [3 x - 1]}{{(3 x - 1)}^{2}}$

Step 5.2

Since $3$ is constant with respect to $x$ , the derivative of $3 x$ with respect to $x$ is $3 \frac{d}{d x} [x]$ .

$\frac{3 x - 1}{3 x + 1} \cdot \frac{(3 x - 1) (3 \frac{d}{d x} [x] + \frac{d}{d x} [1]) - (3 x + 1) \frac{d}{d x} [3 x - 1]}{{(3 x - 1)}^{2}}$

Step 5.3

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

$\frac{3 x - 1}{3 x + 1} \cdot \frac{(3 x - 1) (3 \cdot 1 + \frac{d}{d x} [1]) - (3 x + 1) \frac{d}{d x} [3 x - 1]}{{(3 x - 1)}^{2}}$

Step 5.4

Multiply $3$ by $1$ .

$\frac{3 x - 1}{3 x + 1} \cdot \frac{(3 x - 1) (3 + \frac{d}{d x} [1]) - (3 x + 1) \frac{d}{d x} [3 x - 1]}{{(3 x - 1)}^{2}}$

Step 5.5

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

$\frac{3 x - 1}{3 x + 1} \cdot \frac{(3 x - 1) (3 + 0) - (3 x + 1) \frac{d}{d x} [3 x - 1]}{{(3 x - 1)}^{2}}$

Step 5.6

Simplify the expression.

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Step 5.6.1

Add $3$ and $0$ .

$\frac{3 x - 1}{3 x + 1} \cdot \frac{(3 x - 1) \cdot 3 - (3 x + 1) \frac{d}{d x} [3 x - 1]}{{(3 x - 1)}^{2}}$

Step 5.6.2

Move $3$ to the left of $3 x - 1$ .

$\frac{3 x - 1}{3 x + 1} \cdot \frac{3 \cdot (3 x - 1) - (3 x + 1) \frac{d}{d x} [3 x - 1]}{{(3 x - 1)}^{2}}$

Step 5.7

By the Sum Rule, the derivative of $3 x - 1$ with respect to $x$ is $\frac{d}{d x} [3 x] + \frac{d}{d x} [- 1]$ .

$\frac{3 x - 1}{3 x + 1} \cdot \frac{3 (3 x - 1) - (3 x + 1) (\frac{d}{d x} [3 x] + \frac{d}{d x} [- 1])}{{(3 x - 1)}^{2}}$

Step 5.8

Since $3$ is constant with respect to $x$ , the derivative of $3 x$ with respect to $x$ is $3 \frac{d}{d x} [x]$ .

$\frac{3 x - 1}{3 x + 1} \cdot \frac{3 (3 x - 1) - (3 x + 1) (3 \frac{d}{d x} [x] + \frac{d}{d x} [- 1])}{{(3 x - 1)}^{2}}$

Step 5.9

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

$\frac{3 x - 1}{3 x + 1} \cdot \frac{3 (3 x - 1) - (3 x + 1) (3 \cdot 1 + \frac{d}{d x} [- 1])}{{(3 x - 1)}^{2}}$

Step 5.10

Multiply $3$ by $1$ .

$\frac{3 x - 1}{3 x + 1} \cdot \frac{3 (3 x - 1) - (3 x + 1) (3 + \frac{d}{d x} [- 1])}{{(3 x - 1)}^{2}}$

Step 5.11

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

$\frac{3 x - 1}{3 x + 1} \cdot \frac{3 (3 x - 1) - (3 x + 1) (3 + 0)}{{(3 x - 1)}^{2}}$

Step 5.12

Combine fractions.

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Step 5.12.1

Add $3$ and $0$ .

$\frac{3 x - 1}{3 x + 1} \cdot \frac{3 (3 x - 1) - (3 x + 1) \cdot 3}{{(3 x - 1)}^{2}}$

Step 5.12.2

Multiply $3$ by $- 1$ .

$\frac{3 x - 1}{3 x + 1} \cdot \frac{3 (3 x - 1) - 3 (3 x + 1)}{{(3 x - 1)}^{2}}$

Step 5.12.3

Multiply $\frac{3 x - 1}{3 x + 1}$ by $\frac{3 (3 x - 1) - 3 (3 x + 1)}{{(3 x - 1)}^{2}}$ .

$\frac{(3 x - 1) (3 (3 x - 1) - 3 (3 x + 1))}{(3 x + 1) {(3 x - 1)}^{2}}$

Step 6

Cancel the common factors.

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Step 6.1

Factor $3 x - 1$ out of $(3 x + 1) {(3 x - 1)}^{2}$ .

$\frac{(3 x - 1) (3 (3 x - 1) - 3 (3 x + 1))}{(3 x - 1) ((3 x + 1) (3 x - 1))}$

Step 6.2

Cancel the common factor.

$\frac{(3 x - 1) (3 (3 x - 1) - 3 (3 x + 1))}{(3 x - 1) ((3 x + 1) (3 x - 1))}$

Step 6.3

Rewrite the expression.

$\frac{3 (3 x - 1) - 3 (3 x + 1)}{(3 x + 1) (3 x - 1)}$

Step 7

Simplify.

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Step 7.1

Apply the distributive property.

$\frac{3 (3 x) + 3 \cdot - 1 - 3 (3 x + 1)}{(3 x + 1) (3 x - 1)}$

Step 7.2

Apply the distributive property.

$\frac{3 (3 x) + 3 \cdot - 1 - 3 (3 x) - 3 \cdot 1}{(3 x + 1) (3 x - 1)}$

Step 7.3

Simplify the numerator.

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Step 7.3.1

Combine the opposite terms in $3 (3 x) + 3 \cdot - 1 - 3 (3 x) - 3 \cdot 1$ .

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Step 7.3.1.1

Subtract $3 (3 x)$ from $3 (3 x)$ .

$\frac{3 \cdot - 1 + 0 - 3 \cdot 1}{(3 x + 1) (3 x - 1)}$

Step 7.3.1.2

Add $3 \cdot - 1$ and $0$ .

$\frac{3 \cdot - 1 - 3 \cdot 1}{(3 x + 1) (3 x - 1)}$

Step 7.3.2

Simplify each term.

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Step 7.3.2.1

Multiply $3$ by $- 1$ .

$\frac{- 3 - 3 \cdot 1}{(3 x + 1) (3 x - 1)}$

Step 7.3.2.2

Multiply $- 3$ by $1$ .

$\frac{- 3 - 3}{(3 x + 1) (3 x - 1)}$

Step 7.3.3

Subtract $3$ from $- 3$ .

$\frac{- 6}{(3 x + 1) (3 x - 1)}$

Step 7.4

Move the negative in front of the fraction.

$- \frac{6}{(3 x + 1) (3 x - 1)}$