Calculus Examples

$\frac{d y}{d x} = x^{2} e^{4 x}$

Step 1

Rewrite the equation.

$d y = x^{2} e^{4 x} d x$

Step 2

Integrate both sides.

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Step 2.1

Set up an integral on each side.

$\int d y = \int x^{2} e^{4 x} d x$

Step 2.2

Apply the constant rule.

$y + C_{1} = \int x^{2} e^{4 x} d x$

Step 2.3

Integrate the right side.

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Step 2.3.1

Integrate by parts using the formula $\int u d v = u v - \int v d u$ , where $u = x^{2}$ and $d v = e^{4 x}$ .

$y + C_{1} = x^{2} (\frac{1}{4} e^{4 x}) - \int \frac{1}{4} e^{4 x} (2 x) d x$

Step 2.3.2

Simplify.

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Step 2.3.2.1

Combine $\frac{1}{4}$ and $e^{4 x}$ .

$y + C_{1} = x^{2} \frac{e^{4 x}}{4} - \int \frac{1}{4} e^{4 x} (2 x) d x$

Step 2.3.2.2

Combine $x^{2}$ and $\frac{e^{4 x}}{4}$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \int \frac{1}{4} e^{4 x} (2 x) d x$

Step 2.3.3

Since $\frac{1}{4} \cdot 2$ is constant with respect to $x$ , move $\frac{1}{4} \cdot 2$ out of the integral.

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - (\frac{1}{4} \cdot 2 \int e^{4 x} (x) d x)$

Step 2.3.4

Simplify.

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Step 2.3.4.1

Combine $\frac{1}{4}$ and $2$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - (\frac{2}{4} \int e^{4 x} (x) d x)$

Step 2.3.4.2

Cancel the common factor of $2$ and $4$ .

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Step 2.3.4.2.1

Factor $2$ out of $2$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - (\frac{2 (1)}{4} \int e^{4 x} (x) d x)$

Step 2.3.4.2.2

Cancel the common factors.

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Step 2.3.4.2.2.1

Factor $2$ out of $4$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - (\frac{2 \cdot 1}{2 \cdot 2} \int e^{4 x} (x) d x)$

Step 2.3.4.2.2.2

Cancel the common factor.

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - (\frac{2 \cdot 1}{2 \cdot 2} \int e^{4 x} (x) d x)$

Step 2.3.4.2.2.3

Rewrite the expression.

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - (\frac{1}{2} \int e^{4 x} (x) d x)$

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} \int e^{4 x} (x) d x$

Step 2.3.5

Integrate by parts using the formula $\int u d v = u v - \int v d u$ , where $u = x$ and $d v = e^{4 x}$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (x (\frac{1}{4} e^{4 x}) - \int \frac{1}{4} e^{4 x} d x)$

Step 2.3.6

Simplify.

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Step 2.3.6.1

Combine $\frac{1}{4}$ and $e^{4 x}$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (x \frac{e^{4 x}}{4} - \int \frac{1}{4} e^{4 x} d x)$

Step 2.3.6.2

Combine $x$ and $\frac{e^{4 x}}{4}$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \int \frac{1}{4} e^{4 x} d x)$

Step 2.3.6.3

Combine $\frac{1}{4}$ and $e^{4 x}$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \int \frac{e^{4 x}}{4} d x)$

Step 2.3.7

Since $\frac{1}{4}$ is constant with respect to $x$ , move $\frac{1}{4}$ out of the integral.

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - (\frac{1}{4} \int e^{4 x} d x))$

Step 2.3.8

Let $u = 4 x$ . Then $d u = 4 d x$ , so $\frac{1}{4} d u = d x$ . Rewrite using $u$ and $d$ $u$ .

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Step 2.3.8.1

Let $u = 4 x$ . Find $\frac{d u}{d x}$ .

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Step 2.3.8.1.1

Differentiate $4 x$ .

$\frac{d}{d x} [4 x]$

Step 2.3.8.1.2

Since $4$ is constant with respect to $x$ , the derivative of $4 x$ with respect to $x$ is $4 \frac{d}{d x} [x]$ .

$4 \frac{d}{d x} [x]$

Step 2.3.8.1.3

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

$4 \cdot 1$

Step 2.3.8.1.4

Multiply $4$ by $1$ .

$4$

Step 2.3.8.2

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

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{1}{4} \int e^{u} \frac{1}{4} d u)$

Step 2.3.9

Combine $e^{u}$ and $\frac{1}{4}$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{1}{4} \int \frac{e^{u}}{4} d u)$

Step 2.3.10

Since $\frac{1}{4}$ is constant with respect to $u$ , move $\frac{1}{4}$ out of the integral.

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{1}{4} (\frac{1}{4} \int e^{u} d u))$

Step 2.3.11

Simplify.

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Step 2.3.11.1

Multiply $\frac{1}{4}$ by $\frac{1}{4}$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{1}{4 \cdot 4} \int e^{u} d u)$

Step 2.3.11.2

Multiply $4$ by $4$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{1}{16} \int e^{u} d u)$

Step 2.3.12

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

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{1}{16} (e^{u} + C_{2}))$

Step 2.3.13

Simplify.

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Step 2.3.13.1

Rewrite $\frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{1}{16} (e^{u} + C_{2}))$ as $\frac{1}{4} x^{2} e^{4 x} - \frac{1}{2} (\frac{1}{4} x e^{4 x} - \frac{1}{16} e^{u}) + C_{2}$ .

$y + C_{1} = \frac{1}{4} x^{2} e^{4 x} - \frac{1}{2} (\frac{1}{4} x e^{4 x} - \frac{1}{16} e^{u}) + C_{2}$

Step 2.3.13.2

Simplify.

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Step 2.3.13.2.1

Combine $\frac{1}{4}$ and $x^{2}$ .

$y + C_{1} = \frac{x^{2}}{4} e^{4 x} - \frac{1}{2} (\frac{1}{4} x e^{4 x} - \frac{1}{16} e^{u}) + C_{2}$

Step 2.3.13.2.2

Combine $\frac{x^{2}}{4}$ and $e^{4 x}$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{1}{4} x e^{4 x} - \frac{1}{16} e^{u}) + C_{2}$

Step 2.3.13.2.3

Combine $\frac{1}{4}$ and $x$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x}{4} e^{4 x} - \frac{1}{16} e^{u}) + C_{2}$

Step 2.3.13.2.4

Combine $\frac{x}{4}$ and $e^{4 x}$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{1}{16} e^{u}) + C_{2}$

Step 2.3.13.2.5

Combine $e^{u}$ and $\frac{1}{16}$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16}) + C_{2}$

Step 2.3.13.2.6

To write $- \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16})$ as a fraction with a common denominator, multiply by $\frac{4}{4}$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16}) \cdot \frac{4}{4} + C_{2}$

Step 2.3.13.2.7

Combine $- \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16})$ and $\frac{4}{4}$ .

$y + C_{1} = \frac{x^{2} e^{4 x}}{4} + \frac{- \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16}) \cdot 4}{4} + C_{2}$

Step 2.3.13.2.8

Combine the numerators over the common denominator.

$y + C_{1} = \frac{x^{2} e^{4 x} - \frac{1}{2} (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16}) \cdot 4}{4} + C_{2}$

Step 2.3.13.2.9

Multiply $4$ by $- 1$ .

$y + C_{1} = \frac{x^{2} e^{4 x} - 4 (\frac{1}{2}) (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16})}{4} + C_{2}$

Step 2.3.13.2.10

Combine $- 4$ and $\frac{1}{2}$ .

$y + C_{1} = \frac{x^{2} e^{4 x} + \frac{- 4}{2} (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16})}{4} + C_{2}$

Step 2.3.13.2.11

Cancel the common factor of $- 4$ and $2$ .

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Step 2.3.13.2.11.1

Factor $2$ out of $- 4$ .

$y + C_{1} = \frac{x^{2} e^{4 x} + \frac{2 \cdot - 2}{2} (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16})}{4} + C_{2}$

Step 2.3.13.2.11.2

Cancel the common factors.

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Step 2.3.13.2.11.2.1

Factor $2$ out of $2$ .

$y + C_{1} = \frac{x^{2} e^{4 x} + \frac{2 \cdot - 2}{2 (1)} (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16})}{4} + C_{2}$

Step 2.3.13.2.11.2.2

Cancel the common factor.

$y + C_{1} = \frac{x^{2} e^{4 x} + \frac{2 \cdot - 2}{2 \cdot 1} (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16})}{4} + C_{2}$

Step 2.3.13.2.11.2.3

Rewrite the expression.

$y + C_{1} = \frac{x^{2} e^{4 x} + \frac{- 2}{1} (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16})}{4} + C_{2}$

Step 2.3.13.2.11.2.4

Divide $- 2$ by $1$ .

$y + C_{1} = \frac{x^{2} e^{4 x} - 2 (\frac{x e^{4 x}}{4} - \frac{e^{u}}{16})}{4} + C_{2}$

Step 2.3.14

Replace all occurrences of $u$ with $4 x$ .

$y + C_{1} = \frac{x^{2} e^{4 x} - 2 (\frac{x e^{4 x}}{4} - \frac{e^{4 x}}{16})}{4} + C_{2}$

Step 2.3.15

Simplify.

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Step 2.3.15.1

Apply the distributive property.

$y + C_{1} = \frac{x^{2} e^{4 x} - 2 \frac{x e^{4 x}}{4} - 2 (- \frac{e^{4 x}}{16})}{4} + C_{2}$

Step 2.3.15.2

Cancel the common factor of $2$ .

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Step 2.3.15.2.1

Factor $2$ out of $- 2$ .

$y + C_{1} = \frac{x^{2} e^{4 x} + 2 (- 1) \frac{x e^{4 x}}{4} - 2 (- \frac{e^{4 x}}{16})}{4} + C_{2}$

Step 2.3.15.2.2

Factor $2$ out of $4$ .

$y + C_{1} = \frac{x^{2} e^{4 x} + 2 \cdot - 1 \frac{x e^{4 x}}{2 \cdot 2} - 2 (- \frac{e^{4 x}}{16})}{4} + C_{2}$

Step 2.3.15.2.3

Cancel the common factor.

$y + C_{1} = \frac{x^{2} e^{4 x} + 2 \cdot - 1 \frac{x e^{4 x}}{2 \cdot 2} - 2 (- \frac{e^{4 x}}{16})}{4} + C_{2}$

Step 2.3.15.2.4

Rewrite the expression.

$y + C_{1} = \frac{x^{2} e^{4 x} - \frac{x e^{4 x}}{2} - 2 (- \frac{e^{4 x}}{16})}{4} + C_{2}$

Step 2.3.15.3

Cancel the common factor of $2$ .

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Step 2.3.15.3.1

Move the leading negative in $- \frac{e^{4 x}}{16}$ into the numerator.

$y + C_{1} = \frac{x^{2} e^{4 x} - \frac{x e^{4 x}}{2} - 2 \frac{- e^{4 x}}{16}}{4} + C_{2}$

Step 2.3.15.3.2

Factor $2$ out of $- 2$ .

$y + C_{1} = \frac{x^{2} e^{4 x} - \frac{x e^{4 x}}{2} + 2 (- 1) \frac{- e^{4 x}}{16}}{4} + C_{2}$

Step 2.3.15.3.3

Factor $2$ out of $16$ .

$y + C_{1} = \frac{x^{2} e^{4 x} - \frac{x e^{4 x}}{2} + 2 \cdot - 1 \frac{- e^{4 x}}{2 \cdot 8}}{4} + C_{2}$

Step 2.3.15.3.4

Cancel the common factor.

$y + C_{1} = \frac{x^{2} e^{4 x} - \frac{x e^{4 x}}{2} + 2 \cdot - 1 \frac{- e^{4 x}}{2 \cdot 8}}{4} + C_{2}$

Step 2.3.15.3.5

Rewrite the expression.

$y + C_{1} = \frac{x^{2} e^{4 x} - \frac{x e^{4 x}}{2} - \frac{- e^{4 x}}{8}}{4} + C_{2}$

Step 2.3.15.4

Simplify each term.

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Step 2.3.15.4.1

Move the negative in front of the fraction.

$y + C_{1} = \frac{x^{2} e^{4 x} - \frac{x e^{4 x}}{2} - - \frac{e^{4 x}}{8}}{4} + C_{2}$

Step 2.3.15.4.2

Multiply $- - \frac{e^{4 x}}{8}$ .

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Step 2.3.15.4.2.1

Multiply $- 1$ by $- 1$ .

$y + C_{1} = \frac{x^{2} e^{4 x} - \frac{x e^{4 x}}{2} + 1 \frac{e^{4 x}}{8}}{4} + C_{2}$

Step 2.3.15.4.2.2

Multiply $\frac{e^{4 x}}{8}$ by $1$ .

$y + C_{1} = \frac{x^{2} e^{4 x} - \frac{x e^{4 x}}{2} + \frac{e^{4 x}}{8}}{4} + C_{2}$

Step 2.3.16

Reorder terms.

$y + C_{1} = \frac{1}{4} (x^{2} e^{4 x} - \frac{1}{2} x e^{4 x} + \frac{1}{8} e^{4 x}) + C_{2}$

Step 2.4

Group the constant of integration on the right side as $K$ .

$y = \frac{1}{4} (x^{2} e^{4 x} - \frac{1}{2} x e^{4 x} + \frac{1}{8} e^{4 x}) + K$