# How do you solve 5x^2−8x−4=0 using the quadratic formula?

Jun 4, 2016

$x = 2$, $x = - \frac{2}{5}$

#### Explanation:

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

Its roots can be obtained using the equation below

$x = \frac{- b \pm \sqrt{{b}^{2} - 4 a c}}{2 a}$

$5 {x}^{2} - 8 x - 4 = 0$

$\implies x = \frac{- \left(- 8\right) \pm \sqrt{{\left(- 8\right)}^{2} - 4 \left(5\right) \left(- 4\right)}}{2 \left(5\right)}$

$\implies x = \frac{8 \pm \sqrt{64 + 80}}{10}$

$\implies x = \frac{8 \pm \sqrt{144}}{10}$

$\implies x = \frac{8 \pm 12}{10}$

$\implies x = \frac{20}{10} \implies x = 2$
$\implies x = - \frac{4}{10} \implies x = - \frac{2}{5}$