Converging Series for ln(n) with Comparison Tests

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Homework Statement



Find all positive values of b for which the series Ʃ bln(n) converges. Bounds are from n=1 to infinity.

Homework Equations



The assignment is for Direct Comparison Test and Limit Comparison Test.

The Attempt at a Solution



I don't know where to begin. Using a comparison test would only indicate convergence or divergence. It seems like it might be a geometric series, but I'm not sure.
 
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goaliematt76 said:

Homework Statement



Find all positive values of b for which the series Ʃ bln(n) converges. Bounds are from n=1 to infinity.

Homework Equations



The assignment is for Direct Comparison Test and Limit Comparison Test.

The Attempt at a Solution



I don't know where to begin. Using a comparison test would only indicate convergence or divergence. It seems like it might be a geometric series, but I'm not sure.

Try and turn it into a series that looks more familiar. Write b=e^ln(b).
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

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