# How do you solve x^2 - 2x - 15 = 0 using the quadratic formula?

Apr 9, 2016

6 and - 2

#### Explanation:

$y = {x}^{2} - 2 x - 15 = 0$
$D = {d}^{2} = {b}^{2} - 4 a c = 4 + 60 = 64$ --> $d = \pm 8$
$x = - \frac{b}{2 a} \pm \frac{d}{2 a} = \frac{4}{2} \pm \frac{8}{2} = 2 \pm 4$
$x 1 = 2 + 4 = 6$ and $x 2 = 2 - 4 = - 2$