Question

What is the y-value of the vertex of the function f(x) = –(x + 8)(x – 14)?

The y-value of the vertex is
.

Answer 1

121

Explanation:

The function is f(x) = -(x+8)(x-14) and to find the vertex, multiply it out and substitute -b/2a.

`f(x) = -(x+8)(x-14)\\f(x) = -(x^2+8x-14x-112)\\f(x) = -(x^2-6x-112)\\f(x) = -x^2+6x+112`

Here a=1, b=6 and c=112. This means -b/2a = -6/-2= 3.

`f(3) = -(3)^2+6(3)+112 = -9+18+112 = 121`