Math Help - Probability Generating Function

1. Probability Generating Function

Find the Probability generating function of the discrete random variable X with probability mass function

P(X=k)= (2/3)x(1/3)^k-1 for k=1,2...

Hence find the mean of X?

Can anybody help with this question?

2. Re: Probability Generating Function

Hi,
Here's a solution. I hope you understand: