Question

Consider the quadratic function:

Answer 1

Answer:

vertex = (4, - 25 )

Step-by-step explanation:

Given a quadratic function in standard form : f(x) = ax² + bx + c : a ≠ 0

The the x- coordinate of the vertex is

$x_{V}$ = - $\frac{b}{2a}$

f(x) = x² - 8x - 9 ← is in standard form

with a = 1, b = - 8, thus

$x_{V}$ = - $\frac{-8}{2}$ = 4

Substitute x = 4 into f(x) for corresponding value of y

f(4) = 4² - 8(4) - 9 = 16 - 32 - 9 = - 25

vertex = (4, - 25 )

Answer 2

Answer:

vertex is (4,-25)

Step-by-step explanation:

$f(x) = x^2 - 8x - 9$

To find out the vertex we use formula

$x=\frac{-b}{2a}$

From the given f(x), the value of a=1, b=-8 and c=-9

Plug in the values in the formula

$x=\frac{-(-8)}{2(1)}$

x=4

Now find the value of y

plug in 4 for x in f(x)

$f(4) = 4^2 - 8(4)- 9=-25$

The value of y is -25

The vertex is (4,-25)