Calculus Examples

$\int 81 x^{3} e^{3 x} d x$

Step 1

Since $81$ is constant with respect to $x$ , move $81$ out of the integral.

$81 \int x^{3} e^{3 x} d x$

Step 2

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

$81 (x^{3} (\frac{1}{3} e^{3 x}) - \int \frac{1}{3} e^{3 x} (3 x^{2}) d x)$

Step 3

Simplify.

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Step 3.1

Combine $\frac{1}{3}$ and $e^{3 x}$ .

$81 (x^{3} \frac{e^{3 x}}{3} - \int \frac{1}{3} e^{3 x} (3 x^{2}) d x)$

Step 3.2

Combine $x^{3}$ and $\frac{e^{3 x}}{3}$ .

$81 (\frac{x^{3} e^{3 x}}{3} - \int \frac{1}{3} e^{3 x} (3 x^{2}) d x)$

Step 3.3

Combine $\frac{1}{3}$ and $e^{3 x}$ .

$81 (\frac{x^{3} e^{3 x}}{3} - \int \frac{e^{3 x}}{3} (3 x^{2}) d x)$

Step 3.4

Combine $3$ and $\frac{e^{3 x}}{3}$ .

$81 (\frac{x^{3} e^{3 x}}{3} - \int \frac{3 e^{3 x}}{3} x^{2} d x)$

Step 3.5

Combine $\frac{3 e^{3 x}}{3}$ and $x^{2}$ .

$81 (\frac{x^{3} e^{3 x}}{3} - \int \frac{3 e^{3 x} x^{2}}{3} d x)$

Step 3.6

Cancel the common factor of $3$ .

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Step 3.6.1

Cancel the common factor.

$81 (\frac{x^{3} e^{3 x}}{3} - \int \frac{3 e^{3 x} x^{2}}{3} d x)$

Step 3.6.2

Divide $e^{3 x} x^{2}$ by $1$ .

$81 (\frac{x^{3} e^{3 x}}{3} - \int e^{3 x} x^{2} d x)$

Step 4

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

$81 (\frac{x^{3} e^{3 x}}{3} - (x^{2} (\frac{1}{3} e^{3 x}) - \int \frac{1}{3} e^{3 x} (2 x) d x))$

Step 5

Simplify.

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Step 5.1

Combine $\frac{1}{3}$ and $e^{3 x}$ .

$81 (\frac{x^{3} e^{3 x}}{3} - (x^{2} \frac{e^{3 x}}{3} - \int \frac{1}{3} e^{3 x} (2 x) d x))$

Step 5.2

Combine $x^{2}$ and $\frac{e^{3 x}}{3}$ .

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \int \frac{1}{3} e^{3 x} (2 x) d x))$

Step 5.3

Combine $\frac{1}{3}$ and $e^{3 x}$ .

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \int \frac{e^{3 x}}{3} (2 x) d x))$

Step 5.4

Combine $2$ and $\frac{e^{3 x}}{3}$ .

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \int \frac{2 e^{3 x}}{3} x d x))$

Step 5.5

Combine $\frac{2 e^{3 x}}{3}$ and $x$ .

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \int \frac{2 e^{3 x} x}{3} d x))$

Step 6

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

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - (\frac{2}{3} \int e^{3 x} x d x)))$

Step 7

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

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \frac{2}{3} (x (\frac{1}{3} e^{3 x}) - \int \frac{1}{3} e^{3 x} d x)))$

Step 8

Simplify.

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Step 8.1

Combine $\frac{1}{3}$ and $e^{3 x}$ .

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \frac{2}{3} (x \frac{e^{3 x}}{3} - \int \frac{1}{3} e^{3 x} d x)))$

Step 8.2

Combine $x$ and $\frac{e^{3 x}}{3}$ .

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \frac{2}{3} (\frac{x e^{3 x}}{3} - \int \frac{1}{3} e^{3 x} d x)))$

Step 8.3

Combine $\frac{1}{3}$ and $e^{3 x}$ .

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \frac{2}{3} (\frac{x e^{3 x}}{3} - \int \frac{e^{3 x}}{3} d x)))$

Step 9

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

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \frac{2}{3} (\frac{x e^{3 x}}{3} - (\frac{1}{3} \int e^{3 x} d x))))$

Step 10

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

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Step 10.1

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

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Step 10.1.1

Differentiate $3 x$ .

$\frac{d}{d x} [3 x]$

Step 10.1.2

Since $3$ is constant with respect to $x$ , the derivative of $3 x$ with respect to $x$ is $3 \frac{d}{d x} [x]$ .

$3 \frac{d}{d x} [x]$

Step 10.1.3

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

$3 \cdot 1$

Step 10.1.4

Multiply $3$ by $1$ .

$3$

Step 10.2

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

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \frac{2}{3} (\frac{x e^{3 x}}{3} - \frac{1}{3} \int e^{u} \frac{1}{3} d u)))$

Step 11

Combine $e^{u}$ and $\frac{1}{3}$ .

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \frac{2}{3} (\frac{x e^{3 x}}{3} - \frac{1}{3} \int \frac{e^{u}}{3} d u)))$

Step 12

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

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \frac{2}{3} (\frac{x e^{3 x}}{3} - \frac{1}{3} (\frac{1}{3} \int e^{u} d u))))$

Step 13

Simplify.

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Step 13.1

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

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \frac{2}{3} (\frac{x e^{3 x}}{3} - \frac{1}{3 \cdot 3} \int e^{u} d u)))$

Step 13.2

Multiply $3$ by $3$ .

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \frac{2}{3} (\frac{x e^{3 x}}{3} - \frac{1}{9} \int e^{u} d u)))$

Step 14

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

$81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \frac{2}{3} (\frac{x e^{3 x}}{3} - \frac{1}{9} (e^{u} + C))))$

Step 15

Rewrite $81 (\frac{x^{3} e^{3 x}}{3} - (\frac{x^{2} e^{3 x}}{3} - \frac{2}{3} (\frac{x e^{3 x}}{3} - \frac{1}{9} (e^{u} + C))))$ as $81 (\frac{x^{3} e^{3 x}}{3} - \frac{x^{2} e^{3 x}}{3} + \frac{2 x e^{3 x}}{9} - \frac{2 e^{u}}{27}) + C$ .

$81 (\frac{x^{3} e^{3 x}}{3} - \frac{x^{2} e^{3 x}}{3} + \frac{2 x e^{3 x}}{9} - \frac{2 e^{u}}{27}) + C$

Step 16

Replace all occurrences of $u$ with $3 x$ .

$81 (\frac{x^{3} e^{3 x}}{3} - \frac{x^{2} e^{3 x}}{3} + \frac{2 x e^{3 x}}{9} - \frac{2 e^{3 x}}{27}) + C$

Step 17

Simplify.

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Step 17.1

Apply the distributive property.

$81 \frac{x^{3} e^{3 x}}{3} + 81 (- \frac{x^{2} e^{3 x}}{3}) + 81 \frac{2 x e^{3 x}}{9} + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2

Simplify.

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Step 17.2.1

Cancel the common factor of $3$ .

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Step 17.2.1.1

Factor $3$ out of $81$ .

$3 (27) \frac{x^{3} e^{3 x}}{3} + 81 (- \frac{x^{2} e^{3 x}}{3}) + 81 \frac{2 x e^{3 x}}{9} + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2.1.2

Cancel the common factor.

$3 \cdot 27 \frac{x^{3} e^{3 x}}{3} + 81 (- \frac{x^{2} e^{3 x}}{3}) + 81 \frac{2 x e^{3 x}}{9} + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2.1.3

Rewrite the expression.

$27 (x^{3} e^{3 x}) + 81 (- \frac{x^{2} e^{3 x}}{3}) + 81 \frac{2 x e^{3 x}}{9} + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2.2

Cancel the common factor of $3$ .

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Step 17.2.2.1

Move the leading negative in $- \frac{x^{2} e^{3 x}}{3}$ into the numerator.

$27 (x^{3} e^{3 x}) + 81 \frac{- x^{2} e^{3 x}}{3} + 81 \frac{2 x e^{3 x}}{9} + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2.2.2

Factor $3$ out of $81$ .

$27 (x^{3} e^{3 x}) + 3 (27) \frac{- x^{2} e^{3 x}}{3} + 81 \frac{2 x e^{3 x}}{9} + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2.2.3

Cancel the common factor.

$27 (x^{3} e^{3 x}) + 3 \cdot 27 \frac{- x^{2} e^{3 x}}{3} + 81 \frac{2 x e^{3 x}}{9} + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2.2.4

Rewrite the expression.

$27 (x^{3} e^{3 x}) + 27 (- x^{2} e^{3 x}) + 81 \frac{2 x e^{3 x}}{9} + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2.3

Multiply $- 1$ by $27$ .

$27 (x^{3} e^{3 x}) - 27 (x^{2} e^{3 x}) + 81 \frac{2 x e^{3 x}}{9} + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2.4

Cancel the common factor of $9$ .

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Step 17.2.4.1

Factor $9$ out of $81$ .

$27 (x^{3} e^{3 x}) - 27 (x^{2} e^{3 x}) + 9 (9) \frac{2 x e^{3 x}}{9} + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2.4.2

Cancel the common factor.

$27 (x^{3} e^{3 x}) - 27 (x^{2} e^{3 x}) + 9 \cdot 9 \frac{2 x e^{3 x}}{9} + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2.4.3

Rewrite the expression.

$27 (x^{3} e^{3 x}) - 27 (x^{2} e^{3 x}) + 9 (2 x e^{3 x}) + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2.5

Multiply $2$ by $9$ .

$27 (x^{3} e^{3 x}) - 27 (x^{2} e^{3 x}) + 18 (x e^{3 x}) + 81 (- \frac{2 e^{3 x}}{27}) + C$

Step 17.2.6

Cancel the common factor of $27$ .

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Step 17.2.6.1

Move the leading negative in $- \frac{2 e^{3 x}}{27}$ into the numerator.

$27 (x^{3} e^{3 x}) - 27 (x^{2} e^{3 x}) + 18 (x e^{3 x}) + 81 \frac{- 2 e^{3 x}}{27} + C$

Step 17.2.6.2

Factor $27$ out of $81$ .

$27 (x^{3} e^{3 x}) - 27 (x^{2} e^{3 x}) + 18 (x e^{3 x}) + 27 (3) \frac{- 2 e^{3 x}}{27} + C$

Step 17.2.6.3

Cancel the common factor.

$27 (x^{3} e^{3 x}) - 27 (x^{2} e^{3 x}) + 18 (x e^{3 x}) + 27 \cdot 3 \frac{- 2 e^{3 x}}{27} + C$

Step 17.2.6.4

Rewrite the expression.

$27 (x^{3} e^{3 x}) - 27 (x^{2} e^{3 x}) + 18 (x e^{3 x}) + 3 (- 2 e^{3 x}) + C$

Step 17.2.7

Multiply $- 2$ by $3$ .

$27 (x^{3} e^{3 x}) - 27 (x^{2} e^{3 x}) + 18 (x e^{3 x}) - 6 e^{3 x} + C$

Step 17.3

Remove parentheses.

$27 x^{3} e^{3 x} - 27 x^{2} e^{3 x} + 18 x e^{3 x} - 6 e^{3 x} + C$