Answer:
(-7,4)
Explanation:
goal: (y-k)^2=4p(x-h)
y^2-8y=4x+12 Rearranged and added 4x and 12 on both sides
y^2-8y+(-8/2)^2=4x+12+(-8/2)^2 complete square time (add same thing on both sides)
y^2-8y+(-4)^2=4x+12+(-4)^2 (simplify inside the squares)
(y-4)^2=4x+12+16 (now write the left hand side as a square)
(y-4)^2=4x+28
(y-4)^2=4(x+7) factored...
vertex is (-7,4)