Answer:
vertex = ( 4 , 25 )
Step-by-step explanation:
given a parabola in standard form y = a x 2 + b x + c x ; a ≠ 0
then the x-coordinate of the vertex is
X vertex=-b/2a
y=-x2+8x+9 with a=-1 b=8 c=9
X vertex= -8/-2=4
substitute the value on the equation
Y vertex = -(4)squared+8(4)+9=25
