hello :
f(x) = a(x-k)²+k....... the point vertex is (h , k )
in this exercice : h = -3 and k = -1 s0 f(x) = a(x+3)²-1
find : a
but f(0)=8
a(0+3)² -1 = 8
9a-1=8
9a =9
a=1
f(x) =(x+3)²-1 =x²+6x+9-1
f(x) = x²+6x+8 .... (the quadratic function in standard form )
