# How do you solve x^2 + 16x + 64 = 81?

Mar 21, 2018

$x = 1 , - 17$

#### Explanation:

rearrange to the form

$a {x}^{2} + b x + c = 0$

then factorise

${x}^{2} + 16 x + 64 = 81$

${x}^{2} + 16 x - 17 = 0$

$\left(x + 17\right) \left(x - 1\right) = 0$

$\text{ either } x + 17 = 0 \implies x = - 17$

$\text{ or } x - 1 = 0 \implies x = 1$

$\therefore x = 1 , - 17$