IMO 2018 Shortlist A5
Determine all fun tions f : p0,8q Ñ R satisfying ˆ x x ˙ fpyq “ fpxyq f ´y x ¯ for all x,y ą 0. (South Korea)
Category: Algebra
Problem
Determine all fun tions f : p0,8q Ñ R satisfying
ˆ
x x ˙ fpyq “ fpxyq f
´y
x
¯
for all x,y ą 0.
(South Korea)