Question

For f(x) = x^3 – 4x – 7, use the Intermediate Value Theorem to determine which interval
must contain a zero of f.

A. Between 0 and 1
B. Between 1 and 2
C. Between 2 and 3
D. Between 3 and 4

I am leaning towards Choice A. What does everyone think? I would appreciate some feed back! Thanks!

Answer 1

Calculate f(x) at 0,1,2,3 and 4 and see where it changes sign. That will be the answer. There must be a zero of f(x) in that interval, since it is an intermediate value.

By the way, your choice is wrong. f(x) is negative in interval A.

Answer 2

Ok I am trying to figure this out. If A is wrong then my next choice was

C. Between 2 and 3 Is this correct?

Answer 3

Assuming C is correct, could you explain based on what you made this choice?