Answer :

Answer:

9, 20 is the correct answer

Answer:

(9, 20)

Step-by-step explanation:

2 ways to do this:

1) use a graphing calculator and find the vertex off the graph. Vertex is: (9, 20)

2) use the formula x=-b/2a, then substitute the found value of x to find y.

a=-1/3, b = 6, c=-7

x=-6/(2(-1/3)) = -6/(-2/3) = (-6)(2) / (-2) = 9

f(9) = -1/3(9)² + 6(9) - 7 = -27 + 54 - 7 = 20

Vertex is: (9,20)