Could you please give me some hint how to decide about convergence of the series
∑n≥1ln(n+1n)√n ?
I tried using comparison test:
ln(n+1n)√n≥ln(1n)√n=−ln(n)√n.
Series ∑n≥1ln(n)√n diverges by integral test, but for comparison test all compared sequenced must be non-negative and ln(1n)≤0 for all n.
Thanks.
Answer
Yes it does using the asymptotic comparison:
ln(n+1n)√n∼∞1n√n
Remark For the comparison test the general term of the series must have an unchanged sign i.e. not alternating series (no matter positive or negative).
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