Power Series Representation of xln(1+x^2)

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Homework Help Overview

The discussion revolves around finding a power series representation for the function xln(1+x²). Participants are exploring the complexities introduced by the x term and the logarithmic function.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • One participant attempts to derive the series by taking derivatives and integrating, expressing confusion about the convergence of separate summations. Others suggest focusing on the power series expansion of ln(1+u) and its implications for ln(1+x²).

Discussion Status

Some participants are actively engaging with the problem, offering hints and exploring different approaches. There is a recognition of the need for careful thought before posting, indicating a reflective process in understanding the problem.

Contextual Notes

Participants are assuming the expansion is around x=0 and are discussing the implications of this choice on the series representation.

PCSL
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Write a power series representation of xln(1+x2)

My first instinct was to attempt to take the second derivative and then find the summation and then integrate but that approach seemed to be a dead end. Basically, the x thrown in there confuses me and you can't split the function into two separate summations since one would not converge. Any hints..?
 
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Help, anyone?
 
I assume you are expanding around x=0. The power series expansion of x is x. What's the power series expansion of ln(1+u) around u=0? Hence what's the power series expansion of ln(1+x^2). There is no double summation to worry about.
 
Dick said:
I assume you are expanding around x=0. The power series expansion of x is x. What's the power series expansion of ln(1+u) around u=0? Hence what's the power series expansion of ln(1+x^2). There is no double summation to worry about.

I really need to put more thought into problems before posting here. Thanks, and I figured it out.
 

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