Which function in vertex form is equivalent to f (x) = x2 + 8 - 16x?

A. f (x) = (x - 8) 2 - 56

B. f (x) = (x - 4) 2 + 0

C. f (x) = (x + 8) 2 - 72

D. f (x) = (x + 4) 2 - 32

F (x) = x² + 8 - 16x

I'll rearrange it using y and x.

y = x² - 16x + 8

y - 8 = x² - 16x

y - 8 + 64 = x² - 16x + 64

y + 56 = (x-8) ²

y = (x-8) ² - 56

(x - 8) (x - 8) = x (x-8) - 8 (x-8) = x² - 8x - 8x + 64 = x² - 16x + 64

Choice A.) f (x) = (x-8) ² - 56