Power Series Convergence for (5^n)(x-2)^n/8n^7: Explained with Ratio Test

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SUMMARY

The power series defined as Σ (from n=1 to ∞) [(5^n)(x-2)^n]/(8n^7) converges for the condition 5|x-2| < 7. The confusion arises from the application of the ratio test, where the correct interpretation of the series leads to the conclusion that the radius of convergence is determined by the inequality 5|x-2| < 7, not 5|x-2| < 1. This indicates that the series converges within a specific interval around x = 2, which is critical for understanding its behavior.

PREREQUISITES
  • Understanding of power series and their convergence criteria
  • Familiarity with the Ratio Test for convergence
  • Basic knowledge of inequalities and absolute values
  • Concept of radius of convergence in series
NEXT STEPS
  • Study the Ratio Test in detail, focusing on its application to power series
  • Explore the concept of radius of convergence and how it is derived
  • Investigate examples of power series with varying denominators
  • Learn about other convergence tests such as the Root Test and Comparison Test
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Mathematics students, educators, and anyone studying real analysis or series convergence, particularly those working with power series and convergence tests.

cue928
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For the following power series: n=1 to infinity [(5^n)(x-2)^n]/8n^7
I used the ratio test, which I understand, but why does the book say it is convergent for
5|x-2|<7? I had 5|x-2|<1, but I don't understand why it would say 7?
 
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It would be 5|x-2|<7 if it were 7^n in the denominator instead of x^7. Probably a typo in either the question or the answer.
 

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