Calculus Examples

$y = {(\frac{x - 5}{5 x + 1})}^{3}$

Step 1

Differentiate both sides of the equation.

$\frac{d}{d x} (y) = \frac{d}{d x} ({(\frac{x - 5}{5 x + 1})}^{3})$

Step 2

The derivative of $y$ with respect to $x$ is $y'$ .

$y'$

Step 3

Differentiate the right side of the equation.

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Step 3.1

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{3}$ and $g (x) = \frac{x - 5}{5 x + 1}$ .

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Step 3.1.1

To apply the Chain Rule, set $u$ as $\frac{x - 5}{5 x + 1}$ .

$\frac{d}{d u} [u^{3}] \frac{d}{d x} [\frac{x - 5}{5 x + 1}]$

Step 3.1.2

Differentiate using the Power Rule which states that $\frac{d}{d u} [u^{n}]$ is $n u^{n - 1}$ where $n = 3$ .

$3 u^{2} \frac{d}{d x} [\frac{x - 5}{5 x + 1}]$

Step 3.1.3

Replace all occurrences of $u$ with $\frac{x - 5}{5 x + 1}$ .

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{d}{d x} [\frac{x - 5}{5 x + 1}]$

Step 3.2

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 $f (x) = x - 5$ and $g (x) = 5 x + 1$ .

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{(5 x + 1) \frac{d}{d x} [x - 5] - (x - 5) \frac{d}{d x} [5 x + 1]}{{(5 x + 1)}^{2}}$

Step 3.3

Differentiate.

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Step 3.3.1

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

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{(5 x + 1) (\frac{d}{d x} [x] + \frac{d}{d x} [- 5]) - (x - 5) \frac{d}{d x} [5 x + 1]}{{(5 x + 1)}^{2}}$

Step 3.3.2

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

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{(5 x + 1) (1 + \frac{d}{d x} [- 5]) - (x - 5) \frac{d}{d x} [5 x + 1]}{{(5 x + 1)}^{2}}$

Step 3.3.3

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

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{(5 x + 1) (1 + 0) - (x - 5) \frac{d}{d x} [5 x + 1]}{{(5 x + 1)}^{2}}$

Step 3.3.4

Simplify the expression.

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Step 3.3.4.1

Add $1$ and $0$ .

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{(5 x + 1) \cdot 1 - (x - 5) \frac{d}{d x} [5 x + 1]}{{(5 x + 1)}^{2}}$

Step 3.3.4.2

Multiply $5 x + 1$ by $1$ .

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{5 x + 1 - (x - 5) \frac{d}{d x} [5 x + 1]}{{(5 x + 1)}^{2}}$

Step 3.3.5

By the Sum Rule, the derivative of $5 x + 1$ with respect to $x$ is $\frac{d}{d x} [5 x] + \frac{d}{d x} [1]$ .

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{5 x + 1 - (x - 5) (\frac{d}{d x} [5 x] + \frac{d}{d x} [1])}{{(5 x + 1)}^{2}}$

Step 3.3.6

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

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{5 x + 1 - (x - 5) (5 \frac{d}{d x} [x] + \frac{d}{d x} [1])}{{(5 x + 1)}^{2}}$

Step 3.3.7

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

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{5 x + 1 - (x - 5) (5 \cdot 1 + \frac{d}{d x} [1])}{{(5 x + 1)}^{2}}$

Step 3.3.8

Multiply $5$ by $1$ .

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{5 x + 1 - (x - 5) (5 + \frac{d}{d x} [1])}{{(5 x + 1)}^{2}}$

Step 3.3.9

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

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{5 x + 1 - (x - 5) (5 + 0)}{{(5 x + 1)}^{2}}$

Step 3.3.10

Combine fractions.

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Step 3.3.10.1

Add $5$ and $0$ .

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{5 x + 1 - (x - 5) \cdot 5}{{(5 x + 1)}^{2}}$

Step 3.3.10.2

Multiply $5$ by $- 1$ .

$3 {(\frac{x - 5}{5 x + 1})}^{2} \frac{5 x + 1 - 5 (x - 5)}{{(5 x + 1)}^{2}}$

Step 3.3.10.3

Combine $\frac{5 x + 1 - 5 (x - 5)}{{(5 x + 1)}^{2}}$ and $3$ .

$\frac{(5 x + 1 - 5 (x - 5)) \cdot 3}{{(5 x + 1)}^{2}} {(\frac{x - 5}{5 x + 1})}^{2}$

Step 3.3.10.4

Move $3$ to the left of $5 x + 1 - 5 (x - 5)$ .

$\frac{3 \cdot (5 x + 1 - 5 (x - 5))}{{(5 x + 1)}^{2}} {(\frac{x - 5}{5 x + 1})}^{2}$

Step 3.4

Simplify.

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Step 3.4.1

Apply the product rule to $\frac{x - 5}{5 x + 1}$ .

$\frac{3 (5 x + 1 - 5 (x - 5))}{{(5 x + 1)}^{2}} \cdot \frac{{(x - 5)}^{2}}{{(5 x + 1)}^{2}}$

Step 3.4.2

Apply the distributive property.

$\frac{3 (5 x + 1 - 5 x - 5 \cdot - 5)}{{(5 x + 1)}^{2}} \cdot \frac{{(x - 5)}^{2}}{{(5 x + 1)}^{2}}$

Step 3.4.3

Apply the distributive property.

$\frac{3 (5 x) + 3 \cdot 1 + 3 (- 5 x) + 3 (- 5 \cdot - 5)}{{(5 x + 1)}^{2}} \cdot \frac{{(x - 5)}^{2}}{{(5 x + 1)}^{2}}$

Step 3.4.4

Combine terms.

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Step 3.4.4.1

Multiply $5$ by $3$ .

$\frac{15 x + 3 \cdot 1 + 3 (- 5 x) + 3 (- 5 \cdot - 5)}{{(5 x + 1)}^{2}} \cdot \frac{{(x - 5)}^{2}}{{(5 x + 1)}^{2}}$

Step 3.4.4.2

Multiply $3$ by $1$ .

$\frac{15 x + 3 + 3 (- 5 x) + 3 (- 5 \cdot - 5)}{{(5 x + 1)}^{2}} \cdot \frac{{(x - 5)}^{2}}{{(5 x + 1)}^{2}}$

Step 3.4.4.3

Multiply $- 5$ by $3$ .

$\frac{15 x + 3 - 15 x + 3 (- 5 \cdot - 5)}{{(5 x + 1)}^{2}} \cdot \frac{{(x - 5)}^{2}}{{(5 x + 1)}^{2}}$

Step 3.4.4.4

Multiply $- 5$ by $- 5$ .

$\frac{15 x + 3 - 15 x + 3 \cdot 25}{{(5 x + 1)}^{2}} \cdot \frac{{(x - 5)}^{2}}{{(5 x + 1)}^{2}}$

Step 3.4.4.5

Multiply $3$ by $25$ .

$\frac{15 x + 3 - 15 x + 75}{{(5 x + 1)}^{2}} \cdot \frac{{(x - 5)}^{2}}{{(5 x + 1)}^{2}}$

Step 3.4.4.6

Subtract $15 x$ from $15 x$ .

$\frac{0 + 3 + 75}{{(5 x + 1)}^{2}} \cdot \frac{{(x - 5)}^{2}}{{(5 x + 1)}^{2}}$

Step 3.4.4.7

Add $0$ and $3$ .

$\frac{3 + 75}{{(5 x + 1)}^{2}} \cdot \frac{{(x - 5)}^{2}}{{(5 x + 1)}^{2}}$

Step 3.4.4.8

Add $3$ and $75$ .

$\frac{78}{{(5 x + 1)}^{2}} \cdot \frac{{(x - 5)}^{2}}{{(5 x + 1)}^{2}}$

Step 3.4.4.9

Multiply $\frac{78}{{(5 x + 1)}^{2}}$ by $\frac{{(x - 5)}^{2}}{{(5 x + 1)}^{2}}$ .

$\frac{78 {(x - 5)}^{2}}{{(5 x + 1)}^{2} {(5 x + 1)}^{2}}$

Step 3.4.4.10

Multiply ${(5 x + 1)}^{2}$ by ${(5 x + 1)}^{2}$ by adding the exponents.

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Step 3.4.4.10.1

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{78 {(x - 5)}^{2}}{{(5 x + 1)}^{2 + 2}}$

Step 3.4.4.10.2

Add $2$ and $2$ .

$\frac{78 {(x - 5)}^{2}}{{(5 x + 1)}^{4}}$

Step 4

Reform the equation by setting the left side equal to the right side.

$y' = \frac{78 {(x - 5)}^{2}}{{(5 x + 1)}^{4}}$

Step 5

Replace $y'$ with $\frac{d y}{d x}$ .

$\frac{d y}{d x} = \frac{78 {(x - 5)}^{2}}{{(5 x + 1)}^{4}}$