$\displaystyle \sum_{r=1}^{20} \frac{1}{(r+3)(r+6)}$

Help, please?

I'll never understand Series.

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- Mar 24th 2008, 11:53 AMSilverSeries
$\displaystyle \sum_{r=1}^{20} \frac{1}{(r+3)(r+6)}$

Help, please?

I'll never understand Series. - Mar 24th 2008, 12:02 PMThePerfectHacker
$\displaystyle \frac{1}{(k+3)(k+6)} = \frac{1}{3}\left( \frac{ 1 }{k+3} - \frac{1}{k+6}\right)$.

- Mar 24th 2008, 09:17 PMmr fantastic
If you're still stuck after reading TPH's reply, read Telescoping series - Wikipedia, the free encyclopedia