x^2+3x=24, halve the linear coefficient, square it, and add it to both sides
In this case (3/2)^2=2.25
x^2+3x+2.25=26.25 now the left side is a perfect square...
(x+1.5)^2=26.25 take the square root of both sides
x+1.5=±√26.25 subtract 1.5 from both sides
x=-1.5±√26.25
x=-1.5-√26.25 and -1.5+√26.25
x≈ -6.62 and 3.62
