To solve by completing square method we proceed as follows: 2x^2+16x=-18 dividing through by 2 we get: x^2+8x=-9 but c=(-b/2a)^2 c=(-8/2)=16 hence x^2+8x+16=-9+16 x^2+8x+16=7 (x+4)(x+4)=7 (x+4)^2=7 thus getting the square root of both sides x+4=+/-√7 x=-4+/-√7 x=
