Factor 81x^2-16

$81 x^{2} - 16$

Step 1

Rewrite $81 x^{2}$ as ${(9 x)}^{2}$ .

${(9 x)}^{2} - 16$

Step 2

Rewrite $16$ as $4^{2}$ .

${(9 x)}^{2} - 4^{2}$

Step 3

Since both terms are perfect squares, factor using the difference of squares formula, $a^{2} - b^{2} = (a + b) (a - b)$ where $a = 9 x$ and $b = 4$ .

$(9 x + 4) (9 x - 4)$