Taylor Expansion where the derivatives are undefined?

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SUMMARY

The discussion centers on expanding the function x/(x-1) at the point a=1, where the derivatives are undefined. The provided expansion is (x-1)^(-1) + 1, which is identified as a Laurent series rather than a Taylor series due to the singularity at x=1. Participants express confusion regarding the derivation method and the validity of using a Taylor expansion in this context, given the function's undefined nature at the expansion point.

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Homework Statement


Expand x/(x-1) at a=1
The book already gives the expansion but it doesn't explain the process. The expansion it gives is:
x/(x-1) = (1+x-1)/(x-1) = (x-1)^(-1) + 1

Homework Equations


The Attempt at a Solution


I've already solved for the Mclaurin expansion for the same polynomial which gives me -x - x^2 - x^3 - x^4 - ...
The derivatives all have a power of (x-1) as its denominator therefore all of its derivatives are undefined. I don't know any other way to expand polynomials other than term by term, I've been staring at

x/(x-1) = (1+x-1)/(x-1) = (x-1)^(-1) + 1

But it doesn't make sense. All they did was just split the fraction up into two parts.
 
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Are you sure you don't want the Laurent expansion instead of the Taylor expansion?
 
micromass said:
Are you sure you don't want the Laurent expansion instead of the Taylor expansion?

Sorry about that, yes I believe that is the case.
 
Are you confused about how (x-1)-1 + 1 is a Laurent series?
 
Office_Shredder said:
Are you confused about how (x-1)-1 + 1 is a Laurent series?

I'm confused about the method used to derive it. As in I don't understand the method of the reasoning behind it.

Also I don't see how they can come up with that answer when the function x/(x-1) is undefined around x=1.
 

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