Question 800921
Given {{{x^2+12x-85=0}}}


Use the term, {{{(12/2)^2=36}}} and add this to both sides of the equation.


{{{x^2+12x-85+36=36}}}
{{{x^2+12x+36-85=36}}}
{{{x^2+12x+36-85+85=36+85}}}
{{{(x+6)^2=36+85}}}
{{{(x+6)^2=115}}}
{{{x+6=0+- sqrt(115)}}}, the zero included only to make rendering work on this site.
{{{highlight(x=-6+- sqrt(115))}}}