# Math Help - Functional Inequality Proof

1. ## Functional Inequality Proof

Let f: $\Re$ $\rightarrow$ $\Re$

be a real-valued function defined on the set of real numbers that satisfies:

$f(x+y)$ $yf(x)+f(f(x))$

for all real numbers $x$ and $y$. Prove that $f(x)=0$ for all $x$ $0$.

2. ## Re: Functional Inequality Proof

See problem 3 here:

2011 Imo Official Solutions