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f(x)=x^2−x−1


Over which interval does f have an average rate of change of zero?


Choose 1 answer:


(Choice A)


2≤x≤3


(Choice B)


−3≤x≤−2


(Choice C)


−1≤x≤2


(Choice D)


−5≤x≤5

Respuesta :

Correct option is:

Choice C.

Explanation:

We have the following quadratic function:

[tex]f(x)=x^2-x-1[/tex]

We know that at the vertex of a quadratic function we'll have either a maximum or minimum in whose case the Average Rate of Change will be zero.

For any quadratic function the vertex is:

[tex]Vertex:(h,k) \\ \\ \\ h=-\frac{b}{2a} \\ \\ \\ Here: \\ \\ a=1 \\ \\ b=-1 \\ \\ c=-1 \\ \\ \\ x=-\frac{-1}{2(1)} \\ \\ h=\frac{1}{2}=0.5 \\ \\ \\ k=f(-\frac{b}{2a}) \\ \\ k=f(\frac{1}{2})=(0.5)^2-(0.5)-1 \\ \\ k=-\frac{5}{4}=-1.25[/tex]

So at [tex]x=h=0.5[/tex] the function will have an average rate of change of zero. Both Choice C and D meet the requirement because [tex]x=h=0.5[/tex] lies on these intervals , but we'll just choose Choice C since this is the least interval. So:

Correct option is:

Choice C.

Learn more:

Derivative: https://brainly.com/question/13419010

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