Pre-Algebra Examples

$(3 x^{3} - 2 x^{2} - 20 x - 4) \div (x + 3)$

Step 1

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

$x$

$3$

$3 x^{3}$

$2 x^{2}$

$20 x$

$4$

Step 2

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

					$3 x^{2}$
	$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$

Step 3

Multiply the new quotient term by the divisor.

				$3 x^{2}$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			+	$3 x^{3}$	+	$9 x^{2}$

Step 4

The expression needs to be subtracted from the dividend, so change all the signs in $3 x^{3} + 9 x^{2}$

				$3 x^{2}$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			-	$3 x^{3}$	-	$9 x^{2}$

Step 5

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

				$3 x^{2}$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			-	$3 x^{3}$	-	$9 x^{2}$
					-	$11 x^{2}$

Step 6

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

				$3 x^{2}$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			-	$3 x^{3}$	-	$9 x^{2}$
					-	$11 x^{2}$	-	$20 x$

Step 7

Divide the highest order term in the dividend $- 11 x^{2}$ by the highest order term in divisor $x$ .

				$3 x^{2}$	-	$11 x$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			-	$3 x^{3}$	-	$9 x^{2}$
					-	$11 x^{2}$	-	$20 x$

Step 8

Multiply the new quotient term by the divisor.

				$3 x^{2}$	-	$11 x$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			-	$3 x^{3}$	-	$9 x^{2}$
					-	$11 x^{2}$	-	$20 x$
					-	$11 x^{2}$	-	$33 x$

Step 9

The expression needs to be subtracted from the dividend, so change all the signs in $- 11 x^{2} - 33 x$

				$3 x^{2}$	-	$11 x$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			-	$3 x^{3}$	-	$9 x^{2}$
					-	$11 x^{2}$	-	$20 x$
					+	$11 x^{2}$	+	$33 x$

Step 10

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

				$3 x^{2}$	-	$11 x$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			-	$3 x^{3}$	-	$9 x^{2}$
					-	$11 x^{2}$	-	$20 x$
					+	$11 x^{2}$	+	$33 x$
							+	$13 x$

Step 11

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

				$3 x^{2}$	-	$11 x$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			-	$3 x^{3}$	-	$9 x^{2}$
					-	$11 x^{2}$	-	$20 x$
					+	$11 x^{2}$	+	$33 x$
							+	$13 x$	-	$4$

Step 12

Divide the highest order term in the dividend $13 x$ by the highest order term in divisor $x$ .

				$3 x^{2}$	-	$11 x$	+	$13$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			-	$3 x^{3}$	-	$9 x^{2}$
					-	$11 x^{2}$	-	$20 x$
					+	$11 x^{2}$	+	$33 x$
							+	$13 x$	-	$4$

Step 13

Multiply the new quotient term by the divisor.

				$3 x^{2}$	-	$11 x$	+	$13$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			-	$3 x^{3}$	-	$9 x^{2}$
					-	$11 x^{2}$	-	$20 x$
					+	$11 x^{2}$	+	$33 x$
							+	$13 x$	-	$4$
							+	$13 x$	+	$39$

Step 14

The expression needs to be subtracted from the dividend, so change all the signs in $13 x + 39$

				$3 x^{2}$	-	$11 x$	+	$13$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			-	$3 x^{3}$	-	$9 x^{2}$
					-	$11 x^{2}$	-	$20 x$
					+	$11 x^{2}$	+	$33 x$
							+	$13 x$	-	$4$
							-	$13 x$	-	$39$

Step 15

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

				$3 x^{2}$	-	$11 x$	+	$13$
$x$	+	$3$		$3 x^{3}$	-	$2 x^{2}$	-	$20 x$	-	$4$
			-	$3 x^{3}$	-	$9 x^{2}$
					-	$11 x^{2}$	-	$20 x$
					+	$11 x^{2}$	+	$33 x$
							+	$13 x$	-	$4$
							-	$13 x$	-	$39$
									-	$43$

Step 16

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

$3 x^{2} - 11 x + 13 - \frac{43}{x + 3}$