Convergence/Divergence of an infinite series

rdioface
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Homework Statement


Prove the convergence or divergence of the series \Sigma(\frac{n}{2n+3})^{2} using the Direct Comparison Test.


Homework Equations


If series A converges and every term in series B is less than the corresponding term in series A, then series B converges.
If series C diverges and every term in series D is greater than the corresponding term in series C, then series D diverges.


The Attempt at a Solution


I can't think of anything useful to compare it to. Turning either the top or the bottom to 1 doesn't yield anything useful, nor does it behave as a p-series.
 
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hi rdioface! :smile:

(use "left(" and "right)" to automatically get latex brackets the right size :wink:)

always try to simplify by getting things as close to 1 as possible …

in this case, try divdiding top and bottom by n :smile:
 
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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