Answer: D
Explanation:
(x-4)²-20
(x-4)(x-4)-20
(x^2)-8x+16-20
= (x^2)-8x-4
D is the same equation as in the question, just written in another form (they are equal). In this form (vertex), the vertex is (h,k), which is easily found in this equation. The vertex reveals the maximum or minimum. The vertex in this problem is (4,-20) because vertex form is f(x)=a(x-h)^2 + k.