Answer:
vertex = (9, - 1 )
Step-by-step explanation:
Given a quadratic in standard form, y = ax² + bx + c : a ≠ 0
Then the x- coordinate of the vertex is
[tex]x_{vertex}[/tex] = - [tex]\frac{b}{2a}[/tex]
y = x² - 18x + 80 ← is in standard form
with a = 1 and b = - 18, thus
[tex]x_{vertex}[/tex] = - [tex]\frac{-18}{2}[/tex] = 9
Substitute x = 9 into the function for corresponding value of y
y = 9² - 18(9) + 80 = 81 - 162 + 80 = - 1
Vertex = (9, - 1 )
