What is the vertex of g(x)=8x^2-64x

The (x,y) point of the vertex is usually labelled as:
Vertex = (h, k)
h = -b /  2a
h = --64 / 2*8
h = 64 / 16
h = 4


To get “k”, input the “h” value into the equation.
k = 8*(4^2) -64*4
k = 8*(4^2) -64*4
k = 128 -256
k = -128
Vertex = (4, -128)

Were is the diagram?