# How do you multiply (y-7)(y+7)?

Apr 19, 2018

${y}^{2} - {7}^{2}$

#### Explanation:

So here can apply a index rule which is:

$\left(a + b\right) \left(a - b\right) = {a}^{2} - {b}^{2}$

So we just apply these brackets to get:

$\left(y - 7\right) \left(y + 7\right)$

Simplify:

${y}^{2} + 7 y - 7 y - {7}^{2}$

Simplify:

${y}^{2} - {7}^{2}$

Hope this helps!