Answer:
x = 4
x = - 4
Step-by-step explanation:
y = 4x² - 64
y = 4(x² - 4²)
4(x - 4)(x + 4)
Two separate equations
x - 4 = 0
x + 4 = 0
x - 4 + 4 = 0 + 4
x + 4 - 4 = 0 - 4