Question

F(x)=x^2−x−1

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

Choose 1 answer:

(Choice A)

−5≤x≤5

(Choice B)

2≤x≤3

(Choice C)

−3≤x≤−2

(Choice D)

−1≤x≤2

Answer 1

Answer

choice D, you can see it from the airplane, we say in Romania

Explanation

symetric axis is x=-(-1)/2=1/2

it fits only Choice D because interval A is symetric  raport to 0 and both intervals B and C do not even contain 1/2

and of course, yo can verify |-1/2-1|=|2-1/2|

so f(-1)=f(2)=whatever,, we do not need to calculate f(-1) -f(2)=0

Please excuse my English, and please do improove your communication; here we are a site where using " PLEASE " and " Thank you" is an advantage.