Question 939188
the vertex form of a Parabola opening up(a>0) or down(a<0), 
{{{y=a(x-h)^2 +k}}} 
where(h,k) is the vertex  and  x = h  is the Line of Symmetry 
...for Ex
y = -(x-2)^2 + 3 would Open downward V(2,3)max
{{{drawing(300,300,   -6, 6, -6, 6, grid(1), blue(line(2,6,2,-6)) ,
circle(2,3,0.3),
graph( 300, 300, -6, 6, -6, 6,0, -(x-2)^2 + 3) )}}}