A nice functional equation from Romania
18:15
an absolutely surprising final solution to this functional equation.
11:13
A fun functional equation!!
16:41
a fun functional equation with an inverse twist
8:29
A Curious Functional Equation | Math Olympiads
11:41
A nice suggested differential equation
13:09
two nice superfactorial problems
13:26
A Fun One from the Vietnamese IMO
17:56