First you use the formula (-b/2a) to find the axis of symmetry(or the x value) and then you plug that into the equation to find the y value.
a = 2
b= -16
16/2(2)=16/4=4
(4, x ) so we have the x-value and now we plug 4 into the original equation
y=2(4)^2-16(4)+8
y=2(16)-64+8
y=32-64+8
y=-24
So the vertex is at (4,-24)
