Question

F(x)=x^3−9x

Over which interval does f have a positive average rate of change?

Choose 1 answer:

(Choice A)

[-4, -1]

(Choice B)

[-1, 2]

(Choice C)

[-2, 1]

(Choice D)

[-3, 3]

Answer 1

Răspuns:

A if we talk about changes of the function

but usualy, by rate of change, we do understand ΔF(x)/Δx≅F'(x)

and not ΔF(x)

for us, it is very unclear what doers it mean "average rate of change"

and you are using both "F" and "f" for the same function; it is not clear/not corect, because here we use f for F'

so , please, do not expect a proper answer if you are not giving us  proper requierings

Explicație pas cu pas:

f(-4)=-64+36=-28

f(-1)=-1+9=8  

f(-1)>f(-4) choise A is good

we do not need to verify the other ones

but only for us

f(2)=8-18=-10, f(2)<f(-1) we can see Choise B is not good

f(-2) =-f(2)=10

f(1) =-f(-1)=-8 ..also C is not good

f(3) =27-27=0

f(-3) =-f(3)=-0=0   we can see also D is not good

extra

I have use for this Function  that f(-x) =-f(x)  ( "odd function")