Calculus Examples

$\frac{x^{3}}{x + 2}$

Step 1

Write $\frac{x^{3}}{x + 2}$ as a function.

$f (x) = \frac{x^{3}}{x + 2}$

Step 2

The function $F (x)$ can be found by finding the indefinite integral of the derivative $f (x)$ .

$F (x) = \int f (x) d x$

Step 3

Set up the integral to solve.

$F (x) = \int \frac{x^{3}}{x + 2} d x$

Step 4

Divide $x^{3}$ by $x + 2$ .

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Step 4.1

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

$x$

$2$

$x^{3}$

$0 x^{2}$

$0 x$

$0$

Step 4.2

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

					$x^{2}$
	$x$	+	$2$		$x^{3}$	+	$0 x^{2}$	+	$0 x$	+	$0$

Step 4.3

Multiply the new quotient term by the divisor.

				$x^{2}$
$x$	+	$2$		$x^{3}$	+	$0 x^{2}$	+	$0 x$	+	$0$
			+	$x^{3}$	+	$2 x^{2}$

Step 4.4

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

				$x^{2}$
$x$	+	$2$		$x^{3}$	+	$0 x^{2}$	+	$0 x$	+	$0$
			-	$x^{3}$	-	$2 x^{2}$

Step 4.5

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

				$x^{2}$
$x$	+	$2$		$x^{3}$	+	$0 x^{2}$	+	$0 x$	+	$0$
			-	$x^{3}$	-	$2 x^{2}$
					-	$2 x^{2}$

Step 4.6

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

				$x^{2}$
$x$	+	$2$		$x^{3}$	+	$0 x^{2}$	+	$0 x$	+	$0$
			-	$x^{3}$	-	$2 x^{2}$
					-	$2 x^{2}$	+	$0 x$

Step 4.7

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

				$x^{2}$	-	$2 x$
$x$	+	$2$		$x^{3}$	+	$0 x^{2}$	+	$0 x$	+	$0$
			-	$x^{3}$	-	$2 x^{2}$
					-	$2 x^{2}$	+	$0 x$

Step 4.8

Multiply the new quotient term by the divisor.

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

Step 4.9

The expression needs to be subtracted from the dividend, so change all the signs in $- 2 x^{2} - 4 x$

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

Step 4.10

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

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

Step 4.11

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

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

Step 4.12

Divide the highest order term in the dividend $4 x$ by the highest order term in divisor $x$ .

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

Step 4.13

Multiply the new quotient term by the divisor.

				$x^{2}$	-	$2 x$	+	$4$
$x$	+	$2$		$x^{3}$	+	$0 x^{2}$	+	$0 x$	+	$0$
			-	$x^{3}$	-	$2 x^{2}$
					-	$2 x^{2}$	+	$0 x$
					+	$2 x^{2}$	+	$4 x$
							+	$4 x$	+	$0$
							+	$4 x$	+	$8$

Step 4.14

The expression needs to be subtracted from the dividend, so change all the signs in $4 x + 8$

				$x^{2}$	-	$2 x$	+	$4$
$x$	+	$2$		$x^{3}$	+	$0 x^{2}$	+	$0 x$	+	$0$
			-	$x^{3}$	-	$2 x^{2}$
					-	$2 x^{2}$	+	$0 x$
					+	$2 x^{2}$	+	$4 x$
							+	$4 x$	+	$0$
							-	$4 x$	-	$8$

Step 4.15

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

				$x^{2}$	-	$2 x$	+	$4$
$x$	+	$2$		$x^{3}$	+	$0 x^{2}$	+	$0 x$	+	$0$
			-	$x^{3}$	-	$2 x^{2}$
					-	$2 x^{2}$	+	$0 x$
					+	$2 x^{2}$	+	$4 x$
							+	$4 x$	+	$0$
							-	$4 x$	-	$8$
									-	$8$

Step 4.16

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

$\int x^{2} - 2 x + 4 - \frac{8}{x + 2} d x$

Step 5

Split the single integral into multiple integrals.

$\int x^{2} d x + \int - 2 x d x + \int 4 d x + \int - \frac{8}{x + 2} d x$

Step 6

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

$\frac{1}{3} x^{3} + C + \int - 2 x d x + \int 4 d x + \int - \frac{8}{x + 2} d x$

Step 7

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

$\frac{1}{3} x^{3} + C - 2 \int x d x + \int 4 d x + \int - \frac{8}{x + 2} d x$

Step 8

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

$\frac{1}{3} x^{3} + C - 2 (\frac{1}{2} x^{2} + C) + \int 4 d x + \int - \frac{8}{x + 2} d x$

Step 9

Apply the constant rule.

$\frac{1}{3} x^{3} + C - 2 (\frac{1}{2} x^{2} + C) + 4 x + C + \int - \frac{8}{x + 2} d x$

Step 10

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

$\frac{1}{3} x^{3} + C - 2 (\frac{x^{2}}{2} + C) + 4 x + C + \int - \frac{8}{x + 2} d x$

Step 11

Since $- 1$ is constant with respect to $x$ , move $- 1$ out of the integral.

$\frac{1}{3} x^{3} + C - 2 (\frac{x^{2}}{2} + C) + 4 x + C - \int \frac{8}{x + 2} d x$

Step 12

Since $8$ is constant with respect to $x$ , move $8$ out of the integral.

$\frac{1}{3} x^{3} + C - 2 (\frac{x^{2}}{2} + C) + 4 x + C - (8 \int \frac{1}{x + 2} d x)$

Step 13

Multiply $8$ by $- 1$ .

$\frac{1}{3} x^{3} + C - 2 (\frac{x^{2}}{2} + C) + 4 x + C - 8 \int \frac{1}{x + 2} d x$

Step 14

Let $u = x + 2$ . Then $d u = d x$ . Rewrite using $u$ and $d$ $u$ .

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Step 14.1

Let $u = x + 2$ . Find $\frac{d u}{d x}$ .

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Step 14.1.1

Differentiate $x + 2$ .

$\frac{d}{d x} [x + 2]$

Step 14.1.2

By the Sum Rule, the derivative of $x + 2$ with respect to $x$ is $\frac{d}{d x} [x] + \frac{d}{d x} [2]$ .

$\frac{d}{d x} [x] + \frac{d}{d x} [2]$

Step 14.1.3

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

$1 + \frac{d}{d x} [2]$

Step 14.1.4

Since $2$ is constant with respect to $x$ , the derivative of $2$ with respect to $x$ is $0$ .

$1 + 0$

Step 14.1.5

Add $1$ and $0$ .

$1$

Step 14.2

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

$\frac{1}{3} x^{3} + C - 2 (\frac{x^{2}}{2} + C) + 4 x + C - 8 \int \frac{1}{u} d u$

Step 15

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

$\frac{1}{3} x^{3} + C - 2 (\frac{x^{2}}{2} + C) + 4 x + C - 8 (\ln (| u |) + C)$

Step 16

Simplify.

$\frac{x^{3}}{3} - x^{2} + 4 x - 8 \ln (| u |) + C$

Step 17

Replace all occurrences of $u$ with $x + 2$ .

$\frac{x^{3}}{3} - x^{2} + 4 x - 8 \ln (| x + 2 |) + C$

Step 18

Reorder terms.

$\frac{1}{3} x^{3} - x^{2} + 4 x - 8 \ln (| x + 2 |) + C$

Step 19

The answer is the antiderivative of the function $f (x) = \frac{x^{3}}{x + 2}$ .

$F (x) =$ $\frac{1}{3} x^{3} - x^{2} + 4 x - 8 \ln (| x + 2 |) + C$