The standard form for a parabola with a y2 term is

 where (h,k) is the vertex 
   
We can get 

 

in standard form: 

Write y as (y-0)



Factor out 2 on the right:


 
Multiply both sides by 







Compare to



-k=-0,  a=1/2,  -h=+2
 k=0             h=-2

So the vertex is (h,k) = (-2,0), the point where the big dot is
in the graph below:



Edwin