Hi,

I am solving an expectation problem, in which I arrived at the following sum expression to evaluate:

$\displaystyle E\left[\frac{X}{2m-X}\right] = \sum_{x_i=0}^{m} \frac{x_i}{2m-x_i} \cdot \frac{\binom{m}{x_i} \binom{n-m}{m-x_i}}{\binom{n}{m}}$

I'm kinda stuck, could someone give me a hint what to do, or where to look for, to compute the expected value here?

Thanks!