Consider the quadratic function:
f(x) = x2 – 8x – 9
vertex: (startfraction negative b over 2 a endfraction, f (startfraction negative b over 2 a))
what is the vertex of the function?
(
,
)

vertex is (4,-25)

Step-by-step explanation:

To find out the vertex we use formula

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

Plug in the values in the formula

x=4

Now find the value of y

plug in 4 for x in f(x)

The value of y is -25

The vertex is (4,-25)

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

= -

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

with a = 1, b = - 8, thus

= - = 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 )

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