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quasar987
Nov29-04, 05:59 PM
Hi. I am starting the study of series and I don't see how to do this problem.

"Show that

\sum_{n=0}^\infty \frac{1}{(n+a)(n+1+a)} = \frac{1}{a}"

All i got is the decomposition in partial fractions as

\sum_{n=0}^\infty (...) = \sum_{n=0}^\infty \frac{1}{(n+a)} + \sum_{n=0}^\infty \frac{-1}{(n+1+a)}

if these sum converge. I tried seeing a patern in the partial sums to find S_n but it's too difficult so there must be another way.


Any hint/help will be appreciated.

e(ho0n3
Nov29-04, 06:46 PM
Using your partial fractions decomposition and rearranging the terms gives:

\frac{1}{a} - \frac{1}{a+1} + \frac{1}{a+1} - \frac{1}{a+2} + \ldots

It can't be any more obvious now can it.