Power series and finding radius of convergence

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SUMMARY

The discussion centers on finding the radius of convergence for the power series \(\sum_{n=0}^\infty \frac{x^n}{n!}\). Using the Ratio Test, the limit is calculated as \(\lim_{n \to \infty} \frac{|x|}{n+1}\), which approaches 0 for any finite \(x\). Consequently, the radius of convergence \(R\) is determined to be infinite, indicating that the series converges for all real numbers \(x\).

PREREQUISITES
  • Understanding of power series
  • Familiarity with the Ratio Test for convergence
  • Basic knowledge of limits in calculus
  • Experience with factorial notation and its properties
NEXT STEPS
  • Study the application of the Ratio Test in different series
  • Explore the concept of interval of convergence for power series
  • Learn about other convergence tests, such as the Root Test
  • Investigate the properties of exponential functions related to power series
USEFUL FOR

Students studying calculus, particularly those focusing on series and convergence, as well as educators seeking to clarify concepts related to power series and convergence tests.

cowmoo32
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Homework Statement


"Find the radius of convergence and interval of convergence of the series"
[tex]\sum_{n=0}^\infty \frac{x^n}{n!}[/tex]

Homework Equations



Ratio Test

The Attempt at a Solution



[tex]\lim{\substack{n\rightarrow \infty}} |x/n+1|[/tex]
(I can't seem to get the |x/n+1| to move up where it should be)

Here's what I don't understand. What do I do if I have an N left over when I get this far?
 
Last edited:
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After using ration test i get

lim x^(n+1)/(n+1)! *(n)/(x^n)! = (x)/(n+1)

ration of convergence is then n-> infinite |x|/n+1 -> 0

so for every chosen x you will get convergence Then R=infinite

Garret
-------------
Imagination is more important than knowlegde - A.Einstein
 
Thanks man. I just got off the phone with my friend and he told me the same thing. I'm not sure what I was thinking...it's been a long day.
 

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