m (2a Ken Pesyna moved to 4.2a Ken Pesyna: Improperly named originally) |
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Latest revision as of 06:43, 15 October 2008
The E[x] equation you come up with in this problem can be simplified (rid the summation term) by using a differentiated form of the commonly used geometric series equation: $ \sum_{n=0}^\infty r^n = 1/(1-r) $
Now take the derivative with respect to r and you get:
$ \sum_{n=0}^\infty nr^{n-1} = 1/(1-r)^2 $
You can use this equation to simplify your expected value.
