Algebra Examples

$4 y^{2} - 81$

Step 1

Rewrite $4 y^{2}$ as ${(2 y)}^{2}$ .

${(2 y)}^{2} - 81$

Step 2

Rewrite $81$ as $9^{2}$ .

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

Step 3

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

$(2 y + 9) (2 y - 9)$