Answer:
the vertex represents a maximum
Vertex is (4,7)
f(x)=-(x-4)^2+7
Step-by-step explanation:
Given the function [tex]f(x)=-x^2+8x+9[/tex]
Equation is in the form of y=ax^2+bx+c
[tex]a=-1[/tex]
When 'a' is negative, then vertex is maximum
when 'a' is positive, then vertex is minimum
[tex]a=-1[/tex] is negative, so the vertex represents a maximum
[tex]f(x)=-x^2+8x+9[/tex], factor out negative
Take out negative sign in common