Calculus Examples

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

Step 1

Since $3$ is constant with respect to $x$ , move $3$ out of the integral.

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

Step 2

Let $u = x^{3} + 8$ . Then $d u = 3 x^{2} d x$ , so $\frac{1}{3} d u = x^{2} d x$ . Rewrite using $u$ and $d$ $u$ .

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Step 2.1

Let $u = x^{3} + 8$ . Find $\frac{d u}{d x}$ .

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Step 2.1.1

Differentiate $x^{3} + 8$ .

$\frac{d}{d x} [x^{3} + 8]$

Step 2.1.2

By the Sum Rule, the derivative of $x^{3} + 8$ with respect to $x$ is $\frac{d}{d x} [x^{3}] + \frac{d}{d x} [8]$ .

$\frac{d}{d x} [x^{3}] + \frac{d}{d x} [8]$

Step 2.1.3

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

$3 x^{2} + \frac{d}{d x} [8]$

Step 2.1.4

Since $8$ is constant with respect to $x$ , the derivative of $8$ with respect to $x$ is $0$ .

$3 x^{2} + 0$

Step 2.1.5

Add $3 x^{2}$ and $0$ .

$3 x^{2}$

Step 2.2

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

$3 \int \frac{1}{\sqrt{u}} \cdot \frac{1}{3} d u$

Step 3

Simplify.

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Step 3.1

Multiply $\frac{1}{\sqrt{u}}$ by $\frac{1}{3}$ .

$3 \int \frac{1}{\sqrt{u} \cdot 3} d u$

Step 3.2

Move $3$ to the left of $\sqrt{u}$ .

$3 \int \frac{1}{3 \sqrt{u}} d u$

Step 4

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

$3 (\frac{1}{3} \int \frac{1}{\sqrt{u}} d u)$

Step 5

Simplify the expression.

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Step 5.1

Simplify.

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Step 5.1.1

Combine $\frac{1}{3}$ and $3$ .

$\frac{3}{3} \int \frac{1}{\sqrt{u}} d u$

Step 5.1.2

Cancel the common factor of $3$ .

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Step 5.1.2.1

Cancel the common factor.

$\frac{3}{3} \int \frac{1}{\sqrt{u}} d u$

Step 5.1.2.2

Rewrite the expression.

$1 \int \frac{1}{\sqrt{u}} d u$

Step 5.1.3

Multiply $\int \frac{1}{\sqrt{u}} d u$ by $1$ .

$\int \frac{1}{\sqrt{u}} d u$

Step 5.2

Apply basic rules of exponents.

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Step 5.2.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{u}$ as $u^{\frac{1}{2}}$ .

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

Step 5.2.2

Move $u^{\frac{1}{2}}$ out of the denominator by raising it to the $- 1$ power.

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

Step 5.2.3

Multiply the exponents in ${(u^{\frac{1}{2}})}^{- 1}$ .

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Step 5.2.3.1

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$\int u^{\frac{1}{2} \cdot - 1} d u$

Step 5.2.3.2

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

$\int u^{\frac{- 1}{2}} d u$

Step 5.2.3.3

Move the negative in front of the fraction.

$\int u^{- \frac{1}{2}} d u$

Step 6

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

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

Step 7

Replace all occurrences of $u$ with $x^{3} + 8$ .

$2 {(x^{3} + 8)}^{\frac{1}{2}} + C$