Factor 81c^2-4

$81 c^{2} - 4$

Step 1

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

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

Step 2

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

${(9 c)}^{2} - 2^{2}$

Step 3

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

$(9 c + 2) (9 c - 2)$