IMO 2007 Shortlist A4
Find all functions f : R+ → R+ such that f x + f(y) = f(x + y) + f(y) (1) for all x,y ∈ R+ . (Symbol R+ denotes the se...
Category: Algebra
Problem
Find all functions f : R+ → R+ such that f x + f(y) = f(x + y) + f(y) (1) for all x,y ∈ R+ . (Symbol R+ denotes the set of all positive real numbers.) (Thaliand)