Question 317510
The equation is in vertex form,
{{{y=a(x-h)^2+k}}} where (h,k) is the vertex.
The x coordinate of the vertex also specifies the axis of symmetry.
Comparing,
(h,k)=(-8,2)
The axis of symmetry occurs at {{{x=-8}}}.
{{{drawing(300,300,-12,2,-2,12,grid(1),circle(-8,2,.3),blue(line(-8,-20,-8,20)),graph(300,300,-12,2,-2,12,(1/2)*(x+8)^2 + 2))}}}