Let f be any function that maps the set of real numbers into the set of

real numbers. Prove that there exist real numbers x and y such that

$f(x−f(y)) > yf(x)+x$

(I didn't use LaTeX.)

## IMO SL-5(2009)

- Sazid Akhter Turzo
**Posts:**69**Joined:**Sat Feb 18, 2012 9:15 am**Location:**Sirajganj-
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### Re: IMO SL-5(2009)

Why didn't you use LaTeX? It isn't that hard, just put a dollar sign before and after your equation, and done. For advanced symbols,the vocabulary is easy too.

Please read Forum Guide and Rules before you post.

Use $L^AT_EX$, It makes our work a lot easier!

Nur Muhammad Shafiullah | Mahi

Use $L^AT_EX$, It makes our work a lot easier!

Nur Muhammad Shafiullah | Mahi

- nafistiham
**Posts:**829**Joined:**Mon Oct 17, 2011 3:56 pm**Location:**24.758613,90.400161-
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### Re: IMO SL-5(2009)

* just click any equation you see in latex*Mahi* wrote:Why didn't you use LaTeX? It isn't that hard, just put a dollar sign before and after your equation, and done. For advanced symbols,the vocabulary is easy too.

* use the equation editor for learnig

* have a look over the links in '*Mahi*'s signature

it is really easy and looks really beautiful and tidy

\[\sum_{k=0}^{n-1}e^{\frac{2 \pi i k}{n}}=0\]

Using $L^AT_EX$ and following the rules of the forum are very easy but really important, too.Please co-operate.

Using $L^AT_EX$ and following the rules of the forum are very easy but really important, too.Please co-operate.