## progression simplification

Hello everybody.

I have transformed my equation so that I get the following progression: $\sum\limits_{i=0}^n ((\sum\limits_{k=1}^{n-i} z^{k})*x^{i})$
How can I simplify it? I would like to calculate it without the progression. Is that possible?
It has a similiar form in comparison with the binomial equation but I do not have the binomial coefficient.
Thanks for helping!

Thomas