Proving Identity for Generalized Sum S(x)

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SUMMARY

The discussion centers on proving the identity for the generalized sum S(x) defined as S(x) = ∑_{n=0}^{∞} n x^n = x / (1 - x)² for |x| < 1. The user utilized Wolfram Alpha for evaluation and recognized its relation to the geometric series. The key insight for proving this identity involves differentiating the geometric series, which leads to the desired result.

PREREQUISITES
  • Understanding of infinite series and convergence criteria
  • Familiarity with geometric series and their properties
  • Basic knowledge of calculus, specifically differentiation
  • Experience with mathematical software tools like Wolfram Alpha
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  • Study the properties of geometric series and their derivatives
  • Learn how to differentiate power series to derive identities
  • Explore advanced topics in series convergence and divergence
  • Practice using Wolfram Alpha for evaluating complex mathematical expressions
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Students in mathematics, particularly those studying calculus and series, educators teaching mathematical proofs, and anyone interested in advanced series identities.

kreil
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Homework Statement


In order to solve the problem I am working on, I have to prove the following generalized problem,

[tex]S(x)=\sum_{n=0}^{\infty} n x^n =\frac{x}{(x-1)^2}[/tex] for |x|< 1

I evaluated this sum using Wolfram Alpha. Clearly it looks related to the geometric series solution, but I am unsure how to prove this identity. Any ideas to get me started?
 
Physics news on Phys.org
Differentiation of the geometric series
 
Of course, I see it now. Thanks!
 

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