# Poisson distribution formular

b]1. Homework Statement [/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 )

## 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 ?

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