Question 1080163
{{{x^2+3x-28=0}}}
{{{x^2+3x+(3/2)^2-28=(3/2)^2}}}
{{{(x+3/2)^2=9/4+28}}}
{{{(x+3/2)^2=9/4+112/4}}}
{{{(x+3/2)^2=121/4}}}
{{{x+3/2=0 +- 11/2}}}
{{{x=-3/2 +- 11/2}}}
So,
{{{x=8/2}}}
{{{x=4}}} 
and 
{{{x=-14/2}}}
{{{x=-7}}}