This problem is everywhere!
12:31
A Soviet number puzzle.
21:09
Every calculus teacher I know skips this!!
19:30
a notorious functional equation.
21:28
All of the details -- for the Calculus students out there!!!
13:51
so you want a VERY HARD math question?!
11:13
A fun functional equation!!
11:05
the return of one of my favorites!!
21:03