# How do you solve x^2 + 5x + 1 = 0 using the quadratic formula?

##### 1 Answer
Jul 20, 2016

$\frac{- 5 \pm \sqrt{21}}{2}$

#### Explanation:

Use the improved quadratic formula (Google, Yahoo Search).
$D = {d}^{2} = {b}^{2} - 4 a c = 25 - 4 = 21$ --> $d = \pm \sqrt{21}$
There are 2 real roots:
$x = - \frac{b}{2 a} \pm \frac{d}{2 a} = - \frac{5}{2} \pm \frac{\sqrt{21}}{2} = \frac{- 5 \pm \sqrt{21}}{2}$