Question

13. Find the vertex of f(x)=x2 -6x +8 .

a
(3,-1)

b
(-3, 1)

c
(-3,-1)

d
(3, 1)

Answer 1

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Answer:

a (3,-1)

Explanation:

The number that "completes the square" is the square of half the x-coefficient, (-6/2)^2 = 9. Rearranging the given function to include the square trinomial, we have ...

f(x) = x^2 -6x +9 -1 . . . . . . . here, we have 8 = 9 - 1

f(x) = (x -3)^2 -1 . . . . . . . . . . vertex form

Comparing this to the generic vertex form ...

f(x) = (x -h)^2 +k . . . . . . . vertex at (h, k)

we see that h=3 and k=-1.

The vertex is (h, k) = (3, -1).