we have that
the equation
y=a(x-h)^2+k
represent a quadratic equation written in vertex form
where
(h,k) -----> is the vertex of the vertical parabola
and
a ----> is the leading coefficient
if a>0 -----> the parabola opens upward and the vertex is a minimum
if a < 0 ----> the parabola opens downward and the vertex is a maximum