Question

Solve the following quadratic equation by completing the square method.
$x^2+x-20=0$

Answer 1

$x^2+x-20=0$

$x^2+x+\frac{1}{4}-\frac{1}{4}-20=0$

$(x+\frac{1}{2}{)}^2=\frac{81}{4}$

$x+\frac{1}{2}=\pm \sqrt{\frac{81}{4}}$

$x=-\frac{1}{2}\pm \sqrt{\frac{81}{4}}$

$x=-\frac{1}{2}\pm \frac{9}{2}$

on simplifying,

$x=4,-5$