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

Rewrite the function as x² − 16x + 8. Completing the square gives x² − 16x + 64 − 64 + 8 = (x − 8)² − 56, so the equivalent vertex form is f(x) = (x − 8)² − 56, choice A.

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