ax^2+bx+c=0 solve by using completing the square.
So this question is essence establishes the quadratic equation formula
hint:
give yourself an equation such as
3x^2 + 12x + 2 = 0
and whichever step you perform on this equation, do the same thing for a parallel solution to ax^2 + bx + c = 0
Of course you know what you are supposed to come up with, right ?