1999 IMO Problems/Problem 6

Problem

Determine all functions $f:\Bbb{R}\to \Bbb{R}$ such that

$f(x-f(y))-f(f(y))+xf(y)+f(x)-1$

for all real numbers $x,y$ .

This problem needs a solution. If you have a solution for it, please help us out by adding it.

1999 IMO (Problems) • Resources
Preceded by Problem 5	1 • 2 • 3 • 4 • 5 • 6	Followed by Last Question
All IMO Problems and Solutions