Pre-Algebra Examples

$(20 x^{2} - 36 x - 42 + 3 x^{3}) \div (x + 8)$

Step 1

Expand $20 x^{2} - 36 x - 42 + 3 x^{3}$ .

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Step 1.1

Move $- 42$ .

$\frac{20 x^{2} - 36 x + 3 x^{3} - 42}{x + 8}$

Step 1.2

Move $- 36 x$ .

$\frac{20 x^{2} + 3 x^{3} - 36 x - 42}{x + 8}$

Step 1.3

Reorder $20 x^{2}$ and $3 x^{3}$ .

$\frac{3 x^{3} + 20 x^{2} - 36 x - 42}{x + 8}$

Step 2

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

$x$

$8$

$3 x^{3}$

$20 x^{2}$

$36 x$

$42$

Step 3

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

					$3 x^{2}$
	$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$

Step 4

Multiply the new quotient term by the divisor.

				$3 x^{2}$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			+	$3 x^{3}$	+	$24 x^{2}$

Step 5

The expression needs to be subtracted from the dividend, so change all the signs in $3 x^{3} + 24 x^{2}$

				$3 x^{2}$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			-	$3 x^{3}$	-	$24 x^{2}$

Step 6

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

				$3 x^{2}$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			-	$3 x^{3}$	-	$24 x^{2}$
					-	$4 x^{2}$

Step 7

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

				$3 x^{2}$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			-	$3 x^{3}$	-	$24 x^{2}$
					-	$4 x^{2}$	-	$36 x$

Step 8

Divide the highest order term in the dividend $- 4 x^{2}$ by the highest order term in divisor $x$ .

				$3 x^{2}$	-	$4 x$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			-	$3 x^{3}$	-	$24 x^{2}$
					-	$4 x^{2}$	-	$36 x$

Step 9

Multiply the new quotient term by the divisor.

				$3 x^{2}$	-	$4 x$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			-	$3 x^{3}$	-	$24 x^{2}$
					-	$4 x^{2}$	-	$36 x$
					-	$4 x^{2}$	-	$32 x$

Step 10

The expression needs to be subtracted from the dividend, so change all the signs in $- 4 x^{2} - 32 x$

				$3 x^{2}$	-	$4 x$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			-	$3 x^{3}$	-	$24 x^{2}$
					-	$4 x^{2}$	-	$36 x$
					+	$4 x^{2}$	+	$32 x$

Step 11

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

				$3 x^{2}$	-	$4 x$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			-	$3 x^{3}$	-	$24 x^{2}$
					-	$4 x^{2}$	-	$36 x$
					+	$4 x^{2}$	+	$32 x$
							-	$4 x$

Step 12

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

				$3 x^{2}$	-	$4 x$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			-	$3 x^{3}$	-	$24 x^{2}$
					-	$4 x^{2}$	-	$36 x$
					+	$4 x^{2}$	+	$32 x$
							-	$4 x$	-	$42$

Step 13

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

				$3 x^{2}$	-	$4 x$	-	$4$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			-	$3 x^{3}$	-	$24 x^{2}$
					-	$4 x^{2}$	-	$36 x$
					+	$4 x^{2}$	+	$32 x$
							-	$4 x$	-	$42$

Step 14

Multiply the new quotient term by the divisor.

				$3 x^{2}$	-	$4 x$	-	$4$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			-	$3 x^{3}$	-	$24 x^{2}$
					-	$4 x^{2}$	-	$36 x$
					+	$4 x^{2}$	+	$32 x$
							-	$4 x$	-	$42$
							-	$4 x$	-	$32$

Step 15

The expression needs to be subtracted from the dividend, so change all the signs in $- 4 x - 32$

				$3 x^{2}$	-	$4 x$	-	$4$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			-	$3 x^{3}$	-	$24 x^{2}$
					-	$4 x^{2}$	-	$36 x$
					+	$4 x^{2}$	+	$32 x$
							-	$4 x$	-	$42$
							+	$4 x$	+	$32$

Step 16

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

				$3 x^{2}$	-	$4 x$	-	$4$
$x$	+	$8$		$3 x^{3}$	+	$20 x^{2}$	-	$36 x$	-	$42$
			-	$3 x^{3}$	-	$24 x^{2}$
					-	$4 x^{2}$	-	$36 x$
					+	$4 x^{2}$	+	$32 x$
							-	$4 x$	-	$42$
							+	$4 x$	+	$32$
									-	$10$

Step 17

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

$3 x^{2} - 4 x - 4 - \frac{10}{x + 8}$