Sunday, 20 August 2017

real analysis - Proof that limit as n approaches inf of 3ncdotfrac1n!=0 using squeeze theorem

This is a homework question. I'm completely new to epsilon proofs, so I'm pretty bad at them.



I want to prove that 3n1(n!)=0 converges to 0.



Here's where I'm at. By the definition of a limit of a sequence, I want




ϵ>0NN such that 3nn!0∣<ϵ.



Or, I want to use the squeeze theorem to bound it below and above with functions with limits of 0.



I started to try to get an appropriate value for N, but it doesn't seem to work out... I'm using the arbitrarily small ϵ to try to find an N for which 3nn!<ϵ for all n > N. I've just tried doing algebraic manipulation, but I haven't got anywhere.



For the squeeze theorem, I thought of trying to bound the sequence between the sequences xn=1n and zn=0. But I would have to prove that 3nn! is bounded above by 1n, which I'm not sure I know how to do.



If you could tell me which of the two methods would be appropriate and some hints for how to proceed I would appreciate it, thanks.

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