# How do you solve x^2 + 5x - 1 = 0?

Jun 26, 2015

Use the standard formula $x = \frac{- b \pm \sqrt{{b}^{2} - 4 a c}}{2 a}$ to solve an expression $a {x}^{2} + b x + c = 0$

#### Explanation:

In this case $x = \frac{- 5 \pm \sqrt{{5}^{2} - 4 \cdot 1 \cdot \left(- 1\right)}}{2 \cdot 1}$
$x = \frac{- 5 \pm \sqrt{25 + 4}}{2}$
$x = \frac{- 5 \pm \sqrt{29}}{2}$
$x = \frac{- 5 + \sqrt{29}}{2} \mathmr{and} \frac{- 5 - \sqrt{29}}{2}$
Using a calculator gives
$x = - 5 + 5.385$ or $x = - 5 - 5.385$
$x = 0.385$ or $x = - 10.385$