an and bn are sequences of non-negative terms
an+1an≤bn+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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