Answer:
-12
Explanation:
Here the coefficients a, b and c are 4, 8 and -8 respectively.
-b
A formula for the axis of symmetry is x = -------
2a
-8
... which yields x = --------- = -1
2(4)
Evaluating f(x) = 4x^2 + 8x - 8 at x = -1 yields f(-1) = 4(-1)^2 + 8(-1) - 8 = -12.
The y-value of the vertex is -12. Note that the vertex lies right smack on the axis of symmetry.