Find the missing coefficients y=ax^2-10x+c vertex : (-5,20)

Remember, for the x value of the vertex is

so
given
x value of vertex is -5
and



multiply both sides by a
5=-5a
divvide both sides by -5
-1=a
a=-1


comlete the square
remember if we do
(h,k) is the vertex
I know, we can subsitute the known values of te vertex
-5 for h and 20 for k then expand







a=-1
c=-5