Factor ab^3-9ab

$a b^{3} - 9 a b$

Step 1

Factor $a b$ out of $a b^{3} - 9 a b$ .

Factor $a b$ out of $a b^{3}$ .

$a b (b^{2}) - 9 a b$

Factor $a b$ out of $- 9 a b$ .

$a b (b^{2}) + a b (- 9)$

Factor $a b$ out of $a b (b^{2}) + a b (- 9)$ .

$a b (b^{2} - 9)$

Step 2

Rewrite $9$ as $3^{2}$ .

$a b (b^{2} - 3^{2})$

Step 3

Factor.

Since both terms are perfect squares, factor using the difference of squares formula, $a^{2} - b^{2} = (a + b) (a - b)$ where $a = b$ and $b = 3$ .

$a b ((b + 3) (b - 3))$

Remove unnecessary parentheses.

$a b (b + 3) (b - 3)$