Answer:
-12
Step-by-step explanation:
To put the equation into vertex form, you can factor out the leading coefficient, then add and subtract a value equal to the square of half the x-coefficient (inside parentheses).
= 4(x^2 +2x) -8
= 4(x^2 +2x +1) -8 -4
= 4(x +1)^2 -12
The y-value of the vertex is -12.
