Tuesday, 7 June 2016

analysis - If fracan+1anleqfracbn+1bn for all n, prove series properties

an and bn are sequences of non-negative terms



an+1anbn+1bn for all n



If n=1bn converges, prove that n=1an converges




If n=1an diverges, prove that n=1bn diverges



I was thinking of trying the ratio test. For the 1st part, bn converges, which implies that limn(bn+1bn) is less than or equal to 1. If it is less than 1, than the same limit for an+1an is less than one, which implies n=1an converges. But I am not sure what to do about if the limit equals 1.



Thanks for the help

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