Laurent's series for the function $\frac{1}{z^2+z}$ on the annular region $1<|z|<R$

50 Views Asked by At

I am studying alone complex variables cause I'm not having class this year due to this pandemic. Now I started to study Laurent's series and I would love to know the answer of this question just to take a start point to move on with my exercises. If somebody could help me I'll be extremely grateful.

1

There are 1 best solutions below

4
On

This can be done for any $R\gt1$, by writing $1/(z^2+z)=1/z\cdot1/(z+1)=1/z-1/(z+1)=1/z-1/z\cdot1/(1-(-1/z))=1/z-1/z\cdot\sum_{n\ge0}(-1/z)^n$.