Question 1023976
Use a finished standard form as {{{x=a(y-k)+h}}}.
The vertex is (h,k).


{{{x=y^2-6y+8}}}
{{{x=y^2-6y+(6/2)^2-(6/2)^2+8}}}
{{{x=y^2-6y+9-9+8}}}
{{{x=(y-3)^2-9+8}}}
{{{x=(y-3)^2-1}}}
The vertex is  (-1,3).