# Thread: Power Series

1. ## Power Series

Find the power series about the origin of e^-z.

So I know that I need to get this into the form 1/(1-n), but I don't know how...

2. Originally Posted by jzellt
Find the power series about the origin of e^-z.

So I know that I need to get this into the form 1/(1-n), but I don't know how...

Surely, you know that $e^z=\sum_{n=0}^\infty\frac{1}{n!}z^n$, and thus you have $e^{-z}=\sum_{n=0}^\infty\frac{1}{n!}(-z)^n=\sum_{n=0}^\infty \frac{(-1)^n}{n!}z^n$