Answer:
(9, 5)
Explanation:
First, we can use the axis of symmetry formula to find the x value of the vertex.
This formula is: -b/2a
Plug in the b and a values:
-b/2a
-(-18) / 2(1)
18/2
= 9
Then, plug in 9 as x into the equation, and solve for y:
f(x) = x² - 18x + 86
f(9) = 9² - 18(9) + 86
f(9) = 81 - 162 + 86
f(9) = 5
y = 5
So, the vertex is at (9, 5)