Calculus Examples

$\int \frac{3 x^{5} - 2 x^{3} + 5 x^{2} - 2}{x^{3} + 1} d x$

Step 1

Divide $3 x^{5} - 2 x^{3} + 5 x^{2} - 2$ by $x^{3} + 1$ .

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Step 1.1

Set up the polynomials to be divided. If there is not a term for every exponent, insert one with a value of $0$ .

$x^{3}$

$0 x^{2}$

$0 x$

$1$

$3 x^{5}$

$0 x^{4}$

$2 x^{3}$

$5 x^{2}$

$0 x$

$2$

Step 1.2

Divide the highest order term in the dividend $3 x^{5}$ by the highest order term in divisor $x^{3}$ .

$3 x^{2}$

$x^{3}$

$0 x^{2}$

$0 x$

$1$

$3 x^{5}$

$0 x^{4}$

$2 x^{3}$

$5 x^{2}$

$0 x$

$2$

Step 1.3

Multiply the new quotient term by the divisor.

$3 x^{2}$

$x^{3}$

$0 x^{2}$

$0 x$

$1$

$3 x^{5}$

$0 x^{4}$

$2 x^{3}$

$5 x^{2}$

$0 x$

$2$

$3 x^{5}$

$0$

$3 x^{2}$

Step 1.4

The expression needs to be subtracted from the dividend, so change all the signs in $3 x^{5} + 0 + 0 + 3 x^{2}$

$3 x^{2}$

$x^{3}$

$0 x^{2}$

$0 x$

$1$

$3 x^{5}$

$0 x^{4}$

$2 x^{3}$

$5 x^{2}$

$0 x$

$2$

$3 x^{5}$

$0$

$3 x^{2}$

Step 1.5

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

$3 x^{2}$

$x^{3}$

$0 x^{2}$

$0 x$

$1$

$3 x^{5}$

$0 x^{4}$

$2 x^{3}$

$5 x^{2}$

$0 x$

$2$

$3 x^{5}$

$0$

$3 x^{2}$

$2 x^{3}$

$2 x^{2}$

Step 1.6

Pull the next term from the original dividend down into the current dividend.

$3 x^{2}$

$x^{3}$

$0 x^{2}$

$0 x$

$1$

$3 x^{5}$

$0 x^{4}$

$2 x^{3}$

$5 x^{2}$

$0 x$

$2$

$3 x^{5}$

$0$

$3 x^{2}$

$2 x^{3}$

$2 x^{2}$

$0 x$

$2$

Step 1.7

Divide the highest order term in the dividend $- 2 x^{3}$ by the highest order term in divisor $x^{3}$ .

$3 x^{2}$

$0 x$

$2$

$x^{3}$

$0 x^{2}$

$0 x$

$1$

$3 x^{5}$

$0 x^{4}$

$2 x^{3}$

$5 x^{2}$

$0 x$

$2$

$3 x^{5}$

$0$

$3 x^{2}$

$2 x^{3}$

$2 x^{2}$

$0 x$

$2$

Step 1.8

Multiply the new quotient term by the divisor.

								$3 x^{2}$	+	$0 x$	-	$2$
$x^{3}$	+	$0 x^{2}$	+	$0 x$	+	$1$		$3 x^{5}$	+	$0 x^{4}$	-	$2 x^{3}$	+	$5 x^{2}$	+	$0 x$	-	$2$
							-	$3 x^{5}$	-	$0$	-	$0$	-	$3 x^{2}$
											-	$2 x^{3}$	+	$2 x^{2}$	+	$0 x$	-	$2$
											-	$2 x^{3}$	+	$0$	+	$0$	-	$2$

Step 1.9

The expression needs to be subtracted from the dividend, so change all the signs in $- 2 x^{3} + 0 + 0 - 2$

								$3 x^{2}$	+	$0 x$	-	$2$
$x^{3}$	+	$0 x^{2}$	+	$0 x$	+	$1$		$3 x^{5}$	+	$0 x^{4}$	-	$2 x^{3}$	+	$5 x^{2}$	+	$0 x$	-	$2$
							-	$3 x^{5}$	-	$0$	-	$0$	-	$3 x^{2}$
											-	$2 x^{3}$	+	$2 x^{2}$	+	$0 x$	-	$2$
											+	$2 x^{3}$	-	$0$	-	$0$	+	$2$

Step 1.10

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

								$3 x^{2}$	+	$0 x$	-	$2$
$x^{3}$	+	$0 x^{2}$	+	$0 x$	+	$1$		$3 x^{5}$	+	$0 x^{4}$	-	$2 x^{3}$	+	$5 x^{2}$	+	$0 x$	-	$2$
							-	$3 x^{5}$	-	$0$	-	$0$	-	$3 x^{2}$
											-	$2 x^{3}$	+	$2 x^{2}$	+	$0 x$	-	$2$
											+	$2 x^{3}$	-	$0$	-	$0$	+	$2$
													+	$2 x^{2}$	+	$0$	+	$0$

Step 1.11

The final answer is the quotient plus the remainder over the divisor.

$\int 3 x^{2} - 2 + \frac{2 x^{2}}{x^{3} + 1} d x$

Step 2

Split the single integral into multiple integrals.

$\int 3 x^{2} d x + \int - 2 d x + \int \frac{2 x^{2}}{x^{3} + 1} d x$

Step 3

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

$3 \int x^{2} d x + \int - 2 d x + \int \frac{2 x^{2}}{x^{3} + 1} d x$

Step 4

By the Power Rule, the integral of $x^{2}$ with respect to $x$ is $\frac{1}{3} x^{3}$ .

$3 (\frac{1}{3} x^{3} + C) + \int - 2 d x + \int \frac{2 x^{2}}{x^{3} + 1} d x$

Step 5

Apply the constant rule.

$3 (\frac{1}{3} x^{3} + C) - 2 x + C + \int \frac{2 x^{2}}{x^{3} + 1} d x$

Step 6

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

$3 (\frac{x^{3}}{3} + C) - 2 x + C + \int \frac{2 x^{2}}{x^{3} + 1} d x$

Step 7

Since $2$ is constant with respect to $x$ , move $2$ out of the integral.

$3 (\frac{x^{3}}{3} + C) - 2 x + C + 2 \int \frac{x^{2}}{x^{3} + 1} d x$

Step 8

Rewrite $x^{3}$ as ${(x^{3})}^{1}$ .

$3 (\frac{x^{3}}{3} + C) - 2 x + C + 2 \int \frac{x^{2}}{{(x^{3})}^{1} + 1} d x$

Step 9

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

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Step 9.1

Let $u_{1} = x^{3}$ . Find $\frac{d u_{1}}{d x}$ .

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Step 9.1.1

Differentiate $x^{3}$ .

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

Step 9.1.2

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

$3 x^{2}$

Step 9.2

Rewrite the problem using $u_{1}$ and $d u_{1}$ .

$3 (\frac{x^{3}}{3} + C) - 2 x + C + 2 \int \frac{1}{{u_{1}}^{1} + 1} \cdot \frac{1}{3} d u_{1}$

Step 10

Simplify.

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Step 10.1

Simplify.

$3 (\frac{x^{3}}{3} + C) - 2 x + C + 2 \int \frac{1}{u_{1} + 1} \cdot \frac{1}{3} d u_{1}$

Step 10.2

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

$3 (\frac{x^{3}}{3} + C) - 2 x + C + 2 \int \frac{1}{(u_{1} + 1) \cdot 3} d u_{1}$

Step 10.3

Move $3$ to the left of $u_{1} + 1$ .

$3 (\frac{x^{3}}{3} + C) - 2 x + C + 2 \int \frac{1}{3 (u_{1} + 1)} d u_{1}$

Step 11

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

$3 (\frac{x^{3}}{3} + C) - 2 x + C + 2 (\frac{1}{3} \int \frac{1}{u_{1} + 1} d u_{1})$

Step 12

Combine $\frac{1}{3}$ and $2$ .

$3 (\frac{x^{3}}{3} + C) - 2 x + C + \frac{2}{3} \int \frac{1}{u_{1} + 1} d u_{1}$

Step 13

Let $u_{2} = u_{1} + 1$ . Then $d u_{2} = d u_{1}$ . Rewrite using $u_{2}$ and $d$ $u_{2}$ .

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Step 13.1

Let $u_{2} = u_{1} + 1$ . Find $\frac{d u_{2}}{d u_{1}}$ .

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Step 13.1.1

Differentiate $u_{1} + 1$ .

$\frac{d}{d u_{1}} [u_{1} + 1]$

Step 13.1.2

By the Sum Rule, the derivative of $u_{1} + 1$ with respect to $u_{1}$ is $\frac{d}{d u_{1}} [u_{1}] + \frac{d}{d u_{1}} [1]$ .

$\frac{d}{d u_{1}} [u_{1}] + \frac{d}{d u_{1}} [1]$

Step 13.1.3

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

$1 + \frac{d}{d u_{1}} [1]$

Step 13.1.4

Since $1$ is constant with respect to $u_{1}$ , the derivative of $1$ with respect to $u_{1}$ is $0$ .

$1 + 0$

Step 13.1.5

Add $1$ and $0$ .

$1$

Step 13.2

Rewrite the problem using $u_{2}$ and $d u_{2}$ .

$3 (\frac{x^{3}}{3} + C) - 2 x + C + \frac{2}{3} \int \frac{1}{u_{2}} d u_{2}$

Step 14

The integral of $\frac{1}{u_{2}}$ with respect to $u_{2}$ is $\ln (| u_{2} |)$ .

$3 (\frac{x^{3}}{3} + C) - 2 x + C + \frac{2}{3} (\ln (| u_{2} |) + C)$

Step 15

Simplify.

$x^{3} - 2 x + \frac{2}{3} \ln (| u_{2} |) + C$

Step 16

Substitute back in for each integration substitution variable.

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Step 16.1

Replace all occurrences of $u_{2}$ with $u_{1} + 1$ .

$x^{3} - 2 x + \frac{2}{3} \ln (| u_{1} + 1 |) + C$

Step 16.2

Replace all occurrences of $u_{1}$ with $x^{3}$ .

$x^{3} - 2 x + \frac{2}{3} \ln (| x^{3} + 1 |) + C$