1. The problem statement, all variables and given/known data f(x) = (1-p)+pe^-lamdba ; x=0 = [p(e^-lambda)lambda^x]/x! ; x = 1, 2, .... = 0 ; otherwise 2. Relevant equations show that f(x) is a valid probability function 3. The attempt at a solution I think I am supposed to integrate [p(e^-lambda)lambda^x]/x! from 0 to infinity... or is it 1 - infinity? i'm very confused. Could someone help me solve this? Thanks Sorry if my notations are wrong, I'm new.