How do you complete the square to solve 4y^2 + 8y - 36 = 0?

Mar 3, 2018

color(red)(x = 2.1623, - 4.1623

Explanation:

$4 {y}^{2} + 8 y - 36 = 0$

$4 \left({x}^{2} + 2 x - 9\right) = 0$

${x}^{2} + 2 x = 9$

${x}^{2} + 2 x + 1 = 9 + 1 = 10$
${\left(x + 1\right)}^{2} = {\left(\sqrt{10}\right)}^{2}$
$x + 1 = \pm \sqrt{10}$
$x = \pm \sqrt{10} - 1$
color(red)(x = 2.1623, - 4.1623