Monday, October 19, 2015

real analysis - Bounding the Series sumik=1nftykafrac1k(k+1)



Let 0<a<1. I'm trying to figure out whether the following series converges:



k=1ka1k(k+1).




Now it's clear that if a were greater than or equal to 1 then this series would diverge since



k=1k11k(k+1)=k=11(k+1)=k=21k=.



So this makes it a bit hard to think of a bound for the series in question. Any advice?


Answer



0kαk(k+1)1k2α,
and 2α>1.


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