3x^2 + 12x - 4 - 2x^2 + 6x + 7 = ___ (x + ___ )^2 + ___ x^2+18x+3= ___ (x + ___ )^2 + 3 x^2+18x=___(x+___)+ ____ (x+9(cuz 9*2=18)---> (x+9)^2= x^2+18x+81 so answer is 1(x+9)^2+84
