Calculus Examples

$\int x e^{6 x} d x$

Step 1

Integrate by parts using the formula $\int u d v = u v - \int v d u$ , where $u = x$ and $d v = e^{6 x}$ .

$x (\frac{1}{6} e^{6 x}) - \int \frac{1}{6} e^{6 x} d x$

Step 2

Simplify.

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Step 2.1

Combine $\frac{1}{6}$ and $e^{6 x}$ .

$x \frac{e^{6 x}}{6} - \int \frac{1}{6} e^{6 x} d x$

Step 2.2

Combine $x$ and $\frac{e^{6 x}}{6}$ .

$\frac{x e^{6 x}}{6} - \int \frac{1}{6} e^{6 x} d x$

Step 3

Since $\frac{1}{6}$ is constant with respect to $x$ , move $\frac{1}{6}$ out of the integral.

$\frac{x e^{6 x}}{6} - (\frac{1}{6} \int e^{6 x} d x)$

Step 4

Let $u = 6 x$ . Then $d u = 6 d x$ , so $\frac{1}{6} d u = d x$ . Rewrite using $u$ and $d$ $u$ .

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Step 4.1

Let $u = 6 x$ . Find $\frac{d u}{d x}$ .

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Step 4.1.1

Differentiate $6 x$ .

$\frac{d}{d x} [6 x]$

Step 4.1.2

Since $6$ is constant with respect to $x$ , the derivative of $6 x$ with respect to $x$ is $6 \frac{d}{d x} [x]$ .

$6 \frac{d}{d x} [x]$

Step 4.1.3

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

$6 \cdot 1$

Step 4.1.4

Multiply $6$ by $1$ .

$6$

Step 4.2

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

$\frac{x e^{6 x}}{6} - \frac{1}{6} \int e^{u} \frac{1}{6} d u$

Step 5

Combine $e^{u}$ and $\frac{1}{6}$ .

$\frac{x e^{6 x}}{6} - \frac{1}{6} \int \frac{e^{u}}{6} d u$

Step 6

Since $\frac{1}{6}$ is constant with respect to $u$ , move $\frac{1}{6}$ out of the integral.

$\frac{x e^{6 x}}{6} - \frac{1}{6} (\frac{1}{6} \int e^{u} d u)$

Step 7

Simplify.

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Step 7.1

Multiply $\frac{1}{6}$ by $\frac{1}{6}$ .

$\frac{x e^{6 x}}{6} - \frac{1}{6 \cdot 6} \int e^{u} d u$

Step 7.2

Multiply $6$ by $6$ .

$\frac{x e^{6 x}}{6} - \frac{1}{36} \int e^{u} d u$

Step 8

The integral of $e^{u}$ with respect to $u$ is $e^{u}$ .

$\frac{x e^{6 x}}{6} - \frac{1}{36} (e^{u} + C)$

Step 9

Rewrite $\frac{x e^{6 x}}{6} - \frac{1}{36} (e^{u} + C)$ as $\frac{1}{6} x e^{6 x} - \frac{1}{36} e^{u} + C$ .

$\frac{1}{6} x e^{6 x} - \frac{1}{36} e^{u} + C$

Step 10

Replace all occurrences of $u$ with $6 x$ .

$\frac{1}{6} x e^{6 x} - \frac{1}{36} e^{6 x} + C$