Poisson distribution formular

1. Apr 30, 2009

ak123456

b]1. The problem statement, all variables and given/known data[/b]
prove that

$$\sum$$( (e^(-u)) (u(^(x)) )/x! (from x=o to n ) = $$\int$$ ( (e^(-y))(y^n) )dy/n! (from u to infinite )

2. Relevant equations

3. The attempt at a solution
i know that the left is Poisson distribution formular but how to do with the 'sum' ?
and the right one i got a infinite series , use integration by part .but i don not know how to simplicity it .
is there anything else i can use for this question ?

Last edited by a moderator: Jan 7, 2014
2. Apr 30, 2009

Re: proof

any help?