Using the completing-the-square method, rewrite f(x) = x2 4x − 1 in vertex form.

Af(x) = (x +2)^2 + 1

Bf(x) = (x + 2^)2

Cf(x) = (x + 2^)2 + 4

Df(x) = (x + 2)^2 − 5