To complete the square, add the square of half the x-coefficient. .. x^2 +3x +2.25 = 12.25 .. (x +1.5)^2 = 3.5^2 .. x +1.5 = ±3.5 .. x = -1.5 ±3.5 .. x = -5 or 2
You can also solve this by factoring. .. x^2 +3x -10 = 0 .. (x -2)*(x +5) = 0 .. x = 2 or -5