# Quick complex analysis query

• Nov 18th 2007, 11:51 AM
musicmental85
Quick complex analysis query
http://www.mathhelpforum.com/math-he...cons/icon1.gif Quick complex analysis query
Hi, I'm just working through examples for revision and I've come across one that I've worked but not sure if its correct. If anyone could check it would be much appreciated:

Expand 1/z in power series about z=1

Ok you can write 1/z as 1/[1+(z-1)] in this case since expansion is about 1. Then: 1/[1+(z-1)= 1/(1+(z-1)/1)=1[1-(z-1)+(z-1)^2-+....]
oo
=SUM (-1)^k(z-1)^k
k=0

Now is this sufficient for the question or have I left anything vitally important out. I am not great at the subject so I need to make sure anything I'm using as study exercises is working out correctly!
http://www.mathhelpforum.com/math-he...c/progress.gif
• Nov 18th 2007, 12:10 PM
ThePerfectHacker
Quote:

Originally Posted by musicmental85
http://www.mathhelpforum.com/math-he...cons/icon1.gif Quick complex analysis query
Hi, I'm just working through examples for revision and I've come across one that I've worked but not sure if its correct. If anyone could check it would be much appreciated:

Expand 1/z in power series about z=1

\$\displaystyle 1/z = 1/1+(z-1) = 1-(z-1)+(z-1)^2-(z-1)^3+...\$
• Nov 18th 2007, 12:14 PM
musicmental85
Perfect, thats what I thought but I know I'll be looking at it later closer to the exams in january and I don't want to learn something incorrect. I don't even need the sum section then do I?