Answer:
vertex is (4,-25)
Step-by-step explanation:
To find out the vertex we use formula
From the given f(x), the value of a=1, b=-8 and c=-9
Plug in the values in the formula
x=4
Now find the value of y
plug in 4 for x in f(x)
The value of y is -25
The vertex is (4,-25)