Calculus Examples

$\int 8 x^{3} \sqrt{2 x + 1} d x$

Step 1

Since $8$ is constant with respect to $x$ , move $8$ out of the integral.

$8 \int x^{3} \sqrt{2 x + 1} d x$

Step 2

Integrate by parts using the formula $\int u d v = u v - \int v d u$ , where $u = x^{3}$ and $d v = \sqrt{2 x + 1}$ .

$8 (x^{3} (\frac{1}{3} {(2 x + 1)}^{\frac{3}{2}}) - \int \frac{1}{3} {(2 x + 1)}^{\frac{3}{2}} (3 x^{2}) d x)$

Step 3

Simplify.

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Step 3.1

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

$8 (x^{3} \frac{{(2 x + 1)}^{\frac{3}{2}}}{3} - \int \frac{1}{3} {(2 x + 1)}^{\frac{3}{2}} (3 x^{2}) d x)$

Step 3.2

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

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int \frac{1}{3} {(2 x + 1)}^{\frac{3}{2}} (3 x^{2}) d x)$

Step 3.3

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

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int \frac{{(2 x + 1)}^{\frac{3}{2}}}{3} (3 x^{2}) d x)$

Step 3.4

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

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int \frac{3 {(2 x + 1)}^{\frac{3}{2}}}{3} x^{2} d x)$

Step 3.5

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

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int \frac{3 {(2 x + 1)}^{\frac{3}{2}} x^{2}}{3} d x)$

Step 3.6

Cancel the common factor.

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int \frac{3 {(2 x + 1)}^{\frac{3}{2}} x^{2}}{3} d x)$

Step 3.7

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

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int {(2 x + 1)}^{\frac{3}{2}} x^{2} d x)$

Step 4

Let $u_{1} = 2 x + 1$ . Then $d u_{1} = 2 d x$ , so $\frac{1}{2} d u_{1} = d x$ . Rewrite using $u_{1}$ and $d$ $u_{1}$ .

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Step 4.1

Let $u_{1} = 2 x + 1$ . Find $\frac{d u_{1}}{d x}$ .

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Step 4.1.1

Differentiate $2 x + 1$ .

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

Step 4.1.2

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

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

Step 4.1.3

Evaluate $\frac{d}{d x} [2 x]$ .

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Step 4.1.3.1

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

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

Step 4.1.3.2

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

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

Step 4.1.3.3

Multiply $2$ by $1$ .

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

Step 4.1.4

Differentiate using the Constant Rule.

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Step 4.1.4.1

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

$2 + 0$

Step 4.1.4.2

Add $2$ and $0$ .

$2$

Step 4.2

Rewrite the problem using $u_{1}$ and $d u_{1}$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int {u_{1}}^{\frac{3}{2}} {(\frac{u_{1}}{2} - \frac{1}{2})}^{2} \frac{1}{2} d u_{1})$

Step 5

Simplify.

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Step 5.1

Combine $\frac{1}{2}$ and ${u_{1}}^{\frac{3}{2}}$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int \frac{{u_{1}}^{\frac{3}{2}}}{2} {(\frac{u_{1}}{2} - \frac{1}{2})}^{2} d u_{1})$

Step 5.2

Combine $\frac{{u_{1}}^{\frac{3}{2}}}{2}$ and ${(\frac{u_{1}}{2} - \frac{1}{2})}^{2}$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int \frac{{u_{1}}^{\frac{3}{2}} {(\frac{u_{1}}{2} - \frac{1}{2})}^{2}}{2} d u_{1})$

Step 6

Since $\frac{1}{2}$ is constant with respect to $u_{1}$ , move $\frac{1}{2}$ out of the integral.

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - (\frac{1}{2} \int {u_{1}}^{\frac{3}{2}} {(\frac{u_{1}}{2} - \frac{1}{2})}^{2} d u_{1}))$

Step 7

Let $u_{2} = \frac{u_{1}}{2} - \frac{1}{2}$ . Then $d u_{2} = \frac{1}{2} d u_{1}$ , so $2 d u_{2} = d u_{1}$ . Rewrite using $u_{2}$ and $d$ $u_{2}$ .

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Step 7.1

Let $u_{2} = \frac{u_{1}}{2} - \frac{1}{2}$ . Find $\frac{d u_{2}}{d u_{1}}$ .

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Step 7.1.1

Differentiate $\frac{u_{1}}{2} - \frac{1}{2}$ .

$\frac{d}{d u_{1}} [\frac{u_{1}}{2} - \frac{1}{2}]$

Step 7.1.2

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

$\frac{d}{d u_{1}} [\frac{u_{1}}{2}] + \frac{d}{d u_{1}} [- \frac{1}{2}]$

Step 7.1.3

Evaluate $\frac{d}{d u_{1}} [\frac{u_{1}}{2}]$ .

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Step 7.1.3.1

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

$\frac{1}{2} \frac{d}{d u_{1}} [u_{1}] + \frac{d}{d u_{1}} [- \frac{1}{2}]$

Step 7.1.3.2

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

$\frac{1}{2} \cdot 1 + \frac{d}{d u_{1}} [- \frac{1}{2}]$

Step 7.1.3.3

Multiply $\frac{1}{2}$ by $1$ .

$\frac{1}{2} + \frac{d}{d u_{1}} [- \frac{1}{2}]$

Step 7.1.4

Differentiate using the Constant Rule.

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Step 7.1.4.1

Since $- \frac{1}{2}$ is constant with respect to $u_{1}$ , the derivative of $- \frac{1}{2}$ with respect to $u_{1}$ is $0$ .

$\frac{1}{2} + 0$

Step 7.1.4.2

Add $\frac{1}{2}$ and $0$ .

$\frac{1}{2}$

Step 7.2

Rewrite the problem using $u_{2}$ and $d u_{2}$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \frac{1}{2} \int {(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2} \frac{1}{\frac{1}{2}} d u_{2})$

Step 8

Simplify.

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Step 8.1

Multiply by the reciprocal of the fraction to divide by $\frac{1}{2}$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \frac{1}{2} \int {(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2} (1 \cdot 2) d u_{2})$

Step 8.2

Multiply $2$ by $1$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \frac{1}{2} \int {(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2} \cdot 2 d u_{2})$

Step 8.3

Move $2$ to the left of ${(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2}$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \frac{1}{2} \int 2 {(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2} d u_{2})$

Step 9

Since $2$ is constant with respect to $u_{2}$ , move $2$ out of the integral.

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \frac{1}{2} (2 \int {(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2} d u_{2}))$

Step 10

Simplify.

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Step 10.1

Multiply $2$ by $- 1$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - 2 (\frac{1}{2}) \int {(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2} d u_{2})$

Step 10.2

Combine $- 2$ and $\frac{1}{2}$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} + \frac{- 2}{2} \int {(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2} d u_{2})$

Step 10.3

Cancel the common factor of $- 2$ and $2$ .

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Step 10.3.1

Factor $2$ out of $- 2$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} + \frac{2 \cdot - 1}{2} \int {(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2} d u_{2})$

Step 10.3.2

Cancel the common factors.

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Step 10.3.2.1

Factor $2$ out of $2$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} + \frac{2 \cdot - 1}{2 (1)} \int {(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2} d u_{2})$

Step 10.3.2.2

Cancel the common factor.

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} + \frac{2 \cdot - 1}{2 \cdot 1} \int {(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2} d u_{2})$

Step 10.3.2.3

Rewrite the expression.

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} + \frac{- 1}{1} \int {(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2} d u_{2})$

Step 10.3.2.4

Divide $- 1$ by $1$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int {(2 u_{2} + 1)}^{\frac{3}{2}} {u_{2}}^{2} d u_{2})$

Step 11

Let $u_{3} = 2 u_{2} + 1$ . Then $d u_{3} = 2 d u_{2}$ , so $\frac{1}{2} d u_{3} = d u_{2}$ . Rewrite using $u_{3}$ and $d$ $u_{3}$ .

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Step 11.1

Let $u_{3} = 2 u_{2} + 1$ . Find $\frac{d u_{3}}{d u_{2}}$ .

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Step 11.1.1

Differentiate $2 u_{2} + 1$ .

$\frac{d}{d u_{2}} [2 u_{2} + 1]$

Step 11.1.2

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

$\frac{d}{d u_{2}} [2 u_{2}] + \frac{d}{d u_{2}} [1]$

Step 11.1.3

Evaluate $\frac{d}{d u_{2}} [2 u_{2}]$ .

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Step 11.1.3.1

Since $2$ is constant with respect to $u_{2}$ , the derivative of $2 u_{2}$ with respect to $u_{2}$ is $2 \frac{d}{d u_{2}} [u_{2}]$ .

$2 \frac{d}{d u_{2}} [u_{2}] + \frac{d}{d u_{2}} [1]$

Step 11.1.3.2

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

$2 \cdot 1 + \frac{d}{d u_{2}} [1]$

Step 11.1.3.3

Multiply $2$ by $1$ .

$2 + \frac{d}{d u_{2}} [1]$

Step 11.1.4

Differentiate using the Constant Rule.

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Step 11.1.4.1

Since $1$ is constant with respect to $u_{2}$ , the derivative of $1$ with respect to $u_{2}$ is $0$ .

$2 + 0$

Step 11.1.4.2

Add $2$ and $0$ .

$2$

Step 11.2

Rewrite the problem using $u_{3}$ and $d u_{3}$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int {u_{3}}^{\frac{3}{2}} {(\frac{u_{3}}{2} - \frac{1}{2})}^{2} \frac{1}{2} d u_{3})$

Step 12

Simplify.

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Step 12.1

Combine $\frac{1}{2}$ and ${u_{3}}^{\frac{3}{2}}$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int \frac{{u_{3}}^{\frac{3}{2}}}{2} {(\frac{u_{3}}{2} - \frac{1}{2})}^{2} d u_{3})$

Step 12.2

Combine $\frac{{u_{3}}^{\frac{3}{2}}}{2}$ and ${(\frac{u_{3}}{2} - \frac{1}{2})}^{2}$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \int \frac{{u_{3}}^{\frac{3}{2}} {(\frac{u_{3}}{2} - \frac{1}{2})}^{2}}{2} d u_{3})$

Step 13

Since $\frac{1}{2}$ is constant with respect to $u_{3}$ , move $\frac{1}{2}$ out of the integral.

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - (\frac{1}{2} \int {u_{3}}^{\frac{3}{2}} {(\frac{u_{3}}{2} - \frac{1}{2})}^{2} d u_{3}))$

Step 14

Simplify.

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Step 14.1

Rewrite ${(\frac{u_{3}}{2} - \frac{1}{2})}^{2}$ as $(\frac{u_{3}}{2} - \frac{1}{2}) (\frac{u_{3}}{2} - \frac{1}{2})$ .

$8 (\frac{x^{3} {(2 x + 1)}^{\frac{3}{2}}}{3} - \frac{1}{2} \int {u_{3}}^{\frac{3}{2}} ((\frac{u_{3}}{2} - \frac{1}{2}) (\frac{u_{3}}{2} - \frac{1}{2})) d u_{3})$

Step 14.2