How do you solve x^2 - 4x - 5 = 0 by completing the square?

May 31, 2018

Below

Explanation:

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

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

${x}^{2} - 4 x + {\left(\frac{4}{2}\right)}^{2} = 5 + {\left(\frac{4}{2}\right)}^{2}$

${x}^{2} - 4 x + 4 = 5 + 4$

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

$x - 2 = \pm 3$

$x - 2 = 3$ OR $x - 2 = - 3$

$x - 2 = 3$
$x = 5$

$x - 2 = - 3$
$x = - 1$