(2x-8)(2x+8)=(2x-8)2
4x² - 64 = 4x + 16
4x²- 64 - 4x - 16 = 0
4x² - 80 - 4x = 0
x² - 20 - x = 0
x² - x - 20 = 0
x² - 4x - 5x - 20 = 0
x × (x + 4) - 5 (x + 4) = 0
(x+4) (x-5) = 0
x+4=0
x-5=0
x= -4
x= 5
x¹ = -4
x² = 5
