Calculus Examples

$\int \frac{x^{3}}{x + 3} d x$

Step 1

Let $u = x + 3$ . Then $d u = d x$ . Rewrite using $u$ and $d$ $u$ .

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Step 1.1

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

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Step 1.1.1

Differentiate $x + 3$ .

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

Step 1.1.2

By the Sum Rule, the derivative of $x + 3$ with respect to $x$ is $\frac{d}{d x} [x] + \frac{d}{d x} [3]$ .

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

Step 1.1.3

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

$1 + \frac{d}{d x} [3]$

Step 1.1.4

Since $3$ is constant with respect to $x$ , the derivative of $3$ with respect to $x$ is $0$ .

$1 + 0$

Step 1.1.5

Add $1$ and $0$ .

$1$

Step 1.2

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

$\int \frac{{(u - 3)}^{3}}{u} d u$

Step 2

Use the Binomial Theorem.

$\int \frac{u^{3} + 3 u^{2} \cdot - 3 + 3 u {(- 3)}^{2} + {(- 3)}^{3}}{u} d u$

Step 3

Simplify the expression.

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Step 3.1

Rewrite the exponentiation as a product.

$\int \frac{u^{3} + 3 u^{2} \cdot - 3 + 3 u (- 3 \cdot - 3) + {(- 3)}^{3}}{u} d u$

Step 3.2

Rewrite the exponentiation as a product.

$\int \frac{u^{3} + 3 u^{2} \cdot - 3 + 3 u (- 3 \cdot - 3) - 3 {(- 3)}^{2}}{u} d u$

Step 3.3

Rewrite the exponentiation as a product.

$\int \frac{u^{3} + 3 u^{2} \cdot - 3 + 3 u (- 3 \cdot - 3) - 3 (- 3 \cdot - 3)}{u} d u$

Step 3.4

Move $u^{2}$ .

$\int \frac{u^{3} + 3 \cdot - 3 u^{2} + 3 u (- 3 \cdot - 3) - 3 (- 3 \cdot - 3)}{u} d u$

Step 3.5

Move $u$ .

$\int \frac{u^{3} + 3 \cdot - 3 u^{2} + 3 \cdot - 3 \cdot - 3 u - 3 (- 3 \cdot - 3)}{u} d u$

Step 3.6

Multiply $3$ by $- 3$ .

$\int \frac{u^{3} - 9 u^{2} + 3 \cdot - 3 \cdot - 3 u - 3 \cdot - 3 \cdot - 3}{u} d u$

Step 3.7

Multiply $3$ by $- 3$ .

$\int \frac{u^{3} - 9 u^{2} - 9 \cdot - 3 u - 3 \cdot - 3 \cdot - 3}{u} d u$

Step 3.8

Multiply $- 9$ by $- 3$ .

$\int \frac{u^{3} - 9 u^{2} + 27 u - 3 \cdot - 3 \cdot - 3}{u} d u$

Step 3.9

Multiply $- 3$ by $- 3$ .

$\int \frac{u^{3} - 9 u^{2} + 27 u + 9 \cdot - 3}{u} d u$

Step 3.10

Multiply $9$ by $- 3$ .

$\int \frac{u^{3} - 9 u^{2} + 27 u - 27}{u} d u$

Step 4

Divide $u^{3} - 9 u^{2} + 27 u - 27$ by $u$ .

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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 $0$ .

$u$

$0$

$u^{3}$

$9 u^{2}$

$27 u$

$27$

Step 4.2

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

					$u^{2}$
	$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$

Step 4.3

Multiply the new quotient term by the divisor.

				$u^{2}$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			+	$u^{3}$	+	$0$

Step 4.4

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

				$u^{2}$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			-	$u^{3}$	-	$0$

Step 4.5

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

				$u^{2}$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			-	$u^{3}$	-	$0$
					-	$9 u^{2}$

Step 4.6

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

				$u^{2}$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			-	$u^{3}$	-	$0$
					-	$9 u^{2}$	+	$27 u$

Step 4.7

Divide the highest order term in the dividend $- 9 u^{2}$ by the highest order term in divisor $u$ .

				$u^{2}$	-	$9 u$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			-	$u^{3}$	-	$0$
					-	$9 u^{2}$	+	$27 u$

Step 4.8

Multiply the new quotient term by the divisor.

				$u^{2}$	-	$9 u$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			-	$u^{3}$	-	$0$
					-	$9 u^{2}$	+	$27 u$
					-	$9 u^{2}$	+	$0$

Step 4.9

The expression needs to be subtracted from the dividend, so change all the signs in $- 9 u^{2} + 0$

				$u^{2}$	-	$9 u$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			-	$u^{3}$	-	$0$
					-	$9 u^{2}$	+	$27 u$
					+	$9 u^{2}$	-	$0$

Step 4.10

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

				$u^{2}$	-	$9 u$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			-	$u^{3}$	-	$0$
					-	$9 u^{2}$	+	$27 u$
					+	$9 u^{2}$	-	$0$
							+	$27 u$

Step 4.11

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

				$u^{2}$	-	$9 u$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			-	$u^{3}$	-	$0$
					-	$9 u^{2}$	+	$27 u$
					+	$9 u^{2}$	-	$0$
							+	$27 u$	-	$27$

Step 4.12

Divide the highest order term in the dividend $27 u$ by the highest order term in divisor $u$ .

				$u^{2}$	-	$9 u$	+	$27$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			-	$u^{3}$	-	$0$
					-	$9 u^{2}$	+	$27 u$
					+	$9 u^{2}$	-	$0$
							+	$27 u$	-	$27$

Step 4.13

Multiply the new quotient term by the divisor.

				$u^{2}$	-	$9 u$	+	$27$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			-	$u^{3}$	-	$0$
					-	$9 u^{2}$	+	$27 u$
					+	$9 u^{2}$	-	$0$
							+	$27 u$	-	$27$
							+	$27 u$	+	$0$

Step 4.14

The expression needs to be subtracted from the dividend, so change all the signs in $27 u + 0$

				$u^{2}$	-	$9 u$	+	$27$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			-	$u^{3}$	-	$0$
					-	$9 u^{2}$	+	$27 u$
					+	$9 u^{2}$	-	$0$
							+	$27 u$	-	$27$
							-	$27 u$	-	$0$

Step 4.15

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

				$u^{2}$	-	$9 u$	+	$27$
$u$	+	$0$		$u^{3}$	-	$9 u^{2}$	+	$27 u$	-	$27$
			-	$u^{3}$	-	$0$
					-	$9 u^{2}$	+	$27 u$
					+	$9 u^{2}$	-	$0$
							+	$27 u$	-	$27$
							-	$27 u$	-	$0$
									-	$27$

Step 4.16

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

$\int u^{2} - 9 u + 27 - \frac{27}{u} d u$

Step 5

Split the single integral into multiple integrals.

$\int u^{2} d u + \int - 9 u d u + \int 27 d u + \int - \frac{27}{u} d u$

Step 6

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

$\frac{1}{3} u^{3} + C + \int - 9 u d u + \int 27 d u + \int - \frac{27}{u} d u$

Step 7

Since $- 9$ is constant with respect to $u$ , move $- 9$ out of the integral.

$\frac{1}{3} u^{3} + C - 9 \int u d u + \int 27 d u + \int - \frac{27}{u} d u$

Step 8

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

$\frac{1}{3} u^{3} + C - 9 (\frac{1}{2} u^{2} + C) + \int 27 d u + \int - \frac{27}{u} d u$

Step 9

Apply the constant rule.

$\frac{1}{3} u^{3} + C - 9 (\frac{1}{2} u^{2} + C) + 27 u + C + \int - \frac{27}{u} d u$

Step 10

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

$\frac{1}{3} u^{3} + C - 9 (\frac{u^{2}}{2} + C) + 27 u + C + \int - \frac{27}{u} d u$

Step 11

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

$\frac{1}{3} u^{3} + C - 9 (\frac{u^{2}}{2} + C) + 27 u + C - \int \frac{27}{u} d u$

Step 12

Since $27$ is constant with respect to $u$ , move $27$ out of the integral.

$\frac{1}{3} u^{3} + C - 9 (\frac{u^{2}}{2} + C) + 27 u + C - (27 \int \frac{1}{u} d u)$

Step 13

Multiply $27$ by $- 1$ .

$\frac{1}{3} u^{3} + C - 9 (\frac{u^{2}}{2} + C) + 27 u + C - 27 \int \frac{1}{u} d u$

Step 14

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

$\frac{1}{3} u^{3} + C - 9 (\frac{u^{2}}{2} + C) + 27 u + C - 27 (\ln (| u |) + C)$

Step 15

Simplify.

$\frac{u^{3}}{3} - \frac{9 u^{2}}{2} + 27 u - 27 \ln (| u |) + C$

Step 16

Reorder terms.

$\frac{1}{3} u^{3} - \frac{9}{2} u^{2} + 27 u - 27 \ln (| u |) + C$

Step 17

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

$\frac{1}{3} {(x + 3)}^{3} - \frac{9}{2} {(x + 3)}^{2} + 27 (x + 3) - 27 \ln (| x + 3 |) + C$