# Negative Binomial Distribution

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• May 3rd 2010, 12:57 AM
WannaBe
Negative Binomial Distribution
Let $X$~ $NB(r,p)$ when $r>=2$ , $p>0$ .
Calculate: $E[\frac{1}{X-1}]$.
I've tried to get any kind of result by calculating the needed sum but got stuck in the middle...I think there's a better way to do it

Hope you'll be able to help me
Thanks in advance