Y by GrantStar, ehuseyinyigit, OronSH, ohiorizzler1434, NCbutAN
Let
be the set of positive real numbers. Determine all functions
such that
for every
.


![\[x \big(f(x) + f(y)\big) \geqslant \big(f(f(x)) + y\big) f(y)\]](http://latex.artofproblemsolving.com/e/7/1/e71b6e0d0b858eb46b81149f1e6be8c41e13d301.png)

This post has been edited 4 times. Last edited by Scilyse, Feb 11, 2025, 9:51 AM