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- Jan 29, 2012

- 661

I quote an unsolved problem from another forum posted on January 8th, 2013.

I don't know how to solve this problem:

Let f be a continuous real function such that [tex]\{f(x)\} = f(\{x\})[/tex] for each x ([tex]\{x\}[/tex] is the fractional part of number [tex]x[/tex]).

Prove that then [tex]f[/tex] or [tex]f(x)-x[/tex] is a periodic function.

Could you help me?

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