(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A number a is called a fixed point if f(a)=a. Prove that if f is a differentiable function with f'(x)=1 for all x then f has at most one fixed point.

2. Relevant equations

In class we have been using Rolle's Theorem and the Mean Value Theorem.

3. The attempt at a solution

In all honest I wasn't sure where to start but this is what i've come up with so far. Knowing that the slope or f'(x)=1 then the original function must have been something like f(x)= x + k. Considering k as a constant that could exist or could not. Then the function either has no fixed point. Or every point of the function is fixed. Therefore giving us a contradiction in the statement. Meaning that this statement cannot be possible. We worked a couple of these in class and I didn't really know how to approach this problem. What I did kinda makes sense to me although it doesn't seem like this should be the answer. Any help would be appreciated thanks!

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# Mean Value Theorem

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