I have a problem when trying to prove n! >= 2^(n-1). My work: Assuming n=k, k! >= 2^k-1 (induction hypothesis). To prove true for n=k+1, (k+1)! >= 2^(k+1)-1 = 2^k Now considering R.S., 2^k = (2^(k-1))(2) I get stuck here. I don't know how to continue onwards to prove that (k+1)! is >= 2^k. Can anyone show what I did wrong or what I should've done?