告急!!幫我國二數學配方法?

x² + 4x - 64 = 0

x² + 4x = 64

x² + 4x + (4/2)² = 64 + (4/2)²

(x)² + 2(x)(2) + (2)² = 68

(x + 2)² = 68

x + 2 = √68 或 x + 2 = -√68

x + 2 = 2√17 或 x + 2 = -2√17

x = -2 + 2√17 或 x = -2 - 2√17