Tuesday, 23 May 2017

Prove xn converges if xn is a real sequence and sn=fracx0+x1+cdots+xnn+1 converges

Given that xn is a real sequence, sn=x0+x1++xnn+1 and sn converges, an=xnxn1, nan converges to 0, and xnsn=1n+1ni=1iai, prove xn converges, and that xn and sn converge to the same limit.



Since I don't know anything about the sequences increasing, decreasing, or being positive, I was thinking that I can show that 1n+1ni=1iai converges, so then xn will be the sum of two convergent sequences and so it must converge, but I don't know how to show 1n+1ni=1iai converges, or if this is even the right way to go about this problem.



Also since sn converges, it is bounded so maybe I can use that fact, but I'm not sure how that could help.



I also showed that an must converge to 0 as well using the squeeze theorem, but I don't know if that helps either.



Any hints would be great. I have been stuck on this for days.

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