Calculus Examples

$\int x (x^{2} - 2) \cdot 15 d x$

Step 1

Move $15$ to the left of $x (x^{2} - 2)$ .

$\int 15 x (x^{2} - 2) d x$

Step 2

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

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Step 2.1

Let $u = x^{2} - 2$ . Find $\frac{d u}{d x}$ .

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Step 2.1.1

Differentiate $x^{2} - 2$ .

$\frac{d}{d x} [x^{2} - 2]$

Step 2.1.2

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

$\frac{d}{d x} [x^{2}] + \frac{d}{d x} [- 2]$

Step 2.1.3

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

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

Step 2.1.4

Since $- 2$ is constant with respect to $x$ , the derivative of $- 2$ with respect to $x$ is $0$ .

$2 x + 0$

Step 2.1.5

Add $2 x$ and $0$ .

$2 x$

Step 2.2

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

$\int 15 u \frac{1}{2} d u$

Step 3

Simplify.

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Step 3.1

Combine $\frac{1}{2}$ and $15$ .

$\int \frac{15}{2} u d u$

Step 3.2

Combine $\frac{15}{2}$ and $u$ .

$\int \frac{15 u}{2} d u$

Step 4

Since $\frac{15}{2}$ is constant with respect to $u$ , move $\frac{15}{2}$ out of the integral.

$\frac{15}{2} \int u d u$

Step 5

By the Power Rule, the integral of $u$ with respect to $u$ is $\frac{1}{2} u^{2}$ .

$\frac{15}{2} (\frac{1}{2} u^{2} + C)$

Step 6

Simplify.

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Step 6.1

Rewrite $\frac{15}{2} (\frac{1}{2} u^{2} + C)$ as $\frac{15}{2} \cdot \frac{1}{2} u^{2} + C$ .

$\frac{15}{2} \cdot \frac{1}{2} u^{2} + C$

Step 6.2

Simplify.

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Step 6.2.1

Multiply $\frac{15}{2}$ by $\frac{1}{2}$ .

$\frac{15}{2 \cdot 2} u^{2} + C$

Step 6.2.2

Multiply $2$ by $2$ .

$\frac{15}{4} u^{2} + C$

Step 7

Replace all occurrences of $u$ with $x^{2} - 2$ .

$\frac{15}{4} {(x^{2} - 2)}^{2} + C$