Hi, I don't undestand this limits to infinity. [ (2n)! / (n!)^2 ]^1/n and [ ( n^n + 2^n ) / (n! + 3^n) ]^1/n I've absolutely no idea how the first one can be "4", and the seconda one "e". Assuming (1 + 1/n)^n = e I don't see how can I go from that form to this one. Any hint is appreciated.