The webpage title could be: Solving for x in an Infinite Geometric Series

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Discussion Overview

The discussion revolves around solving the equation of an infinite geometric series represented as x + x^2 + x^3 + ... = 14. Participants explore the properties of geometric series and seek clarification on the derivation of formulas related to convergence and summation.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant presents the equation x + x^2 + x^3 + ... = 14 and requests an explanation for solving for x.
  • Another participant cites the formula for the sum of an infinite geometric series, stating 1 + x + x^2 + x^3 + ... = 1/(1-x) for |x| < 1.
  • A participant expresses confusion regarding the formula 1/(x-1) and the conditions for |x| < 1, asking for clarification on geometric series.
  • Another participant provides the finite sum formula 1 + x + x^2 + ... + x^(n-1) = (1 - x^n)/(1-x), explaining its validity for x not equal to 1 and discussing the limit as n approaches infinity.
  • One participant proposes a simpler approach by factoring out x from the series, leading to the equation 15x = 14, suggesting that x = 14/15.

Areas of Agreement / Disagreement

Participants present multiple approaches and interpretations regarding the infinite geometric series and its properties. There is no consensus on a single method for solving the problem, and some participants express confusion about the underlying concepts.

Contextual Notes

Some participants have differing understandings of the convergence criteria and the derivation of the formulas, indicating potential gaps in foundational knowledge or assumptions about the series.

Niaboc67
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x+x^2+x^3+x^4... = 14

Find x

Could someone please provide an explanation.

Thank you
 
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1 + x + x^2 +x^3 + ... = 1/(1-x) for |x| < 1
 
Could you explain why is it 1/(x-1) and for the abs x <1. I don't understand the reason for these and geometric series.
Thanks
 
1 + x + x^2 + ... + x^(n-1) = (1 - x^n)/(1-x)

This expression is valid for all x not equal to 1. Now let n go to infinity. The right side converges to 1/(1-x) if and only if abs(x) < 1 since x^n will goes to 0 for x in the interval (-1,1) and will diverge for x <= -1 or x > 1
 
A simpler way, I think: x+ x^2+ x^3+ ...= 14.
Factor out an x: x(1+ x+ x^2+ x^3+ ...)= x(1+ (x+ x^2+ x^3+ ...))= x(1+ 14)= 15x= 14 so x= 14/15.
 

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