Explain how to solve x2 plus 8x -2 equals 0 by completing a square?

x2 + 8x - 2 = 0 => x2 + 8x = 2 => x2 + 8x + 16 = 2 + 16 = 18 => (x + 4)2 = 18 => x + 4 = +or- sqrt(18) = +or- 3*sqrt(2) so x = -4 +or- 3*sqrt(2)