Calculus Examples

$\int 4 x \sqrt{x - 1} d x$

Step 1

Since $4$ is constant with respect to $x$ , move $4$ out of the integral.

$4 \int x \sqrt{x - 1} d x$

Step 2

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

$4 (x (\frac{2}{3} {(x - 1)}^{\frac{3}{2}}) - \int \frac{2}{3} {(x - 1)}^{\frac{3}{2}} d x)$

Step 3

Simplify.

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Step 3.1

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

$4 (x \frac{2 {(x - 1)}^{\frac{3}{2}}}{3} - \int \frac{2}{3} {(x - 1)}^{\frac{3}{2}} d x)$

Step 3.2

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

$4 (\frac{x (2 {(x - 1)}^{\frac{3}{2}})}{3} - \int \frac{2}{3} {(x - 1)}^{\frac{3}{2}} d x)$

Step 3.3

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

$4 (\frac{x (2 {(x - 1)}^{\frac{3}{2}})}{3} - \int \frac{2 {(x - 1)}^{\frac{3}{2}}}{3} d x)$

Step 4

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

$4 (\frac{x (2 {(x - 1)}^{\frac{3}{2}})}{3} - (\frac{2}{3} \int {(x - 1)}^{\frac{3}{2}} d x))$

Step 5

Let $u = x - 1$ . Then $d u = d x$ . Rewrite using $u$ and $d$ $u$ .

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Step 5.1

Let $u = x - 1$ . Find $\frac{d u}{d x}$ .

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Step 5.1.1

Differentiate $x - 1$ .

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

Step 5.1.2

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

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

Step 5.1.3

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

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

Step 5.1.4

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

$1 + 0$

Step 5.1.5

Add $1$ and $0$ .

$1$

Step 5.2

Rewrite the problem using $u$ and $d u$ .

$4 (\frac{x (2 {(x - 1)}^{\frac{3}{2}})}{3} - \frac{2}{3} \int u^{\frac{3}{2}} d u)$

Step 6

By the Power Rule, the integral of $u^{\frac{3}{2}}$ with respect to $u$ is $\frac{2}{5} u^{\frac{5}{2}}$ .

$4 (\frac{x (2 {(x - 1)}^{\frac{3}{2}})}{3} - \frac{2}{3} (\frac{2}{5} u^{\frac{5}{2}} + C))$

Step 7

Simplify.

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Step 7.1

Combine $\frac{2}{5}$ and $u^{\frac{5}{2}}$ .

$4 (\frac{x (2 {(x - 1)}^{\frac{3}{2}})}{3} - \frac{2}{3} (\frac{2 u^{\frac{5}{2}}}{5} + C))$

Step 7.2

Rewrite $4 (\frac{x (2 {(x - 1)}^{\frac{3}{2}})}{3} - \frac{2}{3} (\frac{2 u^{\frac{5}{2}}}{5} + C))$ as $4 (\frac{2 x {(x - 1)}^{\frac{3}{2}}}{3} - \frac{4 u^{\frac{5}{2}}}{15}) + C$ .

$4 (\frac{2 x {(x - 1)}^{\frac{3}{2}}}{3} - \frac{4 u^{\frac{5}{2}}}{15}) + C$

Step 7.3

Simplify.

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Step 7.3.1

To write $\frac{2 x {(x - 1)}^{\frac{3}{2}}}{3}$ as a fraction with a common denominator, multiply by $\frac{5}{5}$ .

$4 (\frac{2 x {(x - 1)}^{\frac{3}{2}}}{3} \cdot \frac{5}{5} - \frac{4 u^{\frac{5}{2}}}{15}) + C$

Step 7.3.2

Write each expression with a common denominator of $15$ , by multiplying each by an appropriate factor of $1$ .

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Step 7.3.2.1

Multiply $\frac{2 x {(x - 1)}^{\frac{3}{2}}}{3}$ by $\frac{5}{5}$ .

$4 (\frac{2 x {(x - 1)}^{\frac{3}{2}} \cdot 5}{3 \cdot 5} - \frac{4 u^{\frac{5}{2}}}{15}) + C$

Step 7.3.2.2

Multiply $3$ by $5$ .

$4 (\frac{2 x {(x - 1)}^{\frac{3}{2}} \cdot 5}{15} - \frac{4 u^{\frac{5}{2}}}{15}) + C$

Step 7.3.3

Combine the numerators over the common denominator.

$4 \frac{2 x {(x - 1)}^{\frac{3}{2}} \cdot 5 - 4 u^{\frac{5}{2}}}{15} + C$

Step 7.3.4

Multiply $5$ by $2$ .

$4 \frac{10 x {(x - 1)}^{\frac{3}{2}} - 4 u^{\frac{5}{2}}}{15} + C$

Step 7.3.5

Combine $4$ and $\frac{10 x {(x - 1)}^{\frac{3}{2}} - 4 u^{\frac{5}{2}}}{15}$ .

$\frac{4 (10 x {(x - 1)}^{\frac{3}{2}} - 4 u^{\frac{5}{2}})}{15} + C$

Step 8

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

$\frac{4 (10 x {(x - 1)}^{\frac{3}{2}} - 4 {(x - 1)}^{\frac{5}{2}})}{15} + C$

Step 9

Simplify.

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Step 9.1

Apply the distributive property.

$\frac{4 (10 x {(x - 1)}^{\frac{3}{2}}) + 4 (- 4 {(x - 1)}^{\frac{5}{2}})}{15} + C$

Step 9.2

Multiply $10$ by $4$ .

$\frac{40 (x {(x - 1)}^{\frac{3}{2}}) + 4 (- 4 {(x - 1)}^{\frac{5}{2}})}{15} + C$

Step 9.3

Multiply $- 4$ by $4$ .

$\frac{40 x {(x - 1)}^{\frac{3}{2}} - 16 {(x - 1)}^{\frac{5}{2}}}{15} + C$

Step 10

Reorder terms.

$\frac{1}{15} (40 x {(x - 1)}^{\frac{3}{2}} - 16 {(x - 1)}^{\frac{5}{2}}) + C$