Polynomials - Complete the Square Complete the square for x2 + 6x + 8 = -30 Take half of B, and square it, and move C to the other side x2 + 6x + 8 = -30 x2 + 6x + 8-8 = -30-8 x2 + 6x = -38 x2 + 6x + (6/2)2 = -38 - 9 x2 + 6x + 9 = -47 More Examples