Question

what is the y value of the vertex of 4x^2+8x-8

Answer 1

Vertex x=-b/2a
Ax^2+bx+c
X=-8/2 (4)
X=-8/8
X=-1
Plug in
4x^2+8x-8
4 (-1)^2+8 (-1)-8
4 (1)-8-8
4-8-8
-4-8
-12
Vertex= (-1,-12)

Answer 2

Vertex x=-b/2a
Ax^2+bx+c
X=-8/2 (4)
X=-8/8
X=-1
Plug in 
4x^2+8x-8
4 (-1)^2+8 (-1)-8
4 (1)-8-8
4-8-8
-4-8
-12
Vertex= (-1,-12)