Convergent or Divergent? Alternating Series Help for Tomorrow's Test

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Discussion Overview

The discussion centers around determining the convergence of a specific alternating series, expressed as the sum of ((-1)^(n-1)) * ((2n+1)/(n+2)) from 1 to infinity. Participants explore various convergence tests and their applicability, as well as the behavior of the series' terms as n approaches infinity.

Discussion Character

  • Homework-related, Technical explanation, Debate/contested

Main Points Raised

  • One participant expresses difficulty in applying convergence tests, noting that the root test is not applicable, the ratio test yields a limit of 1, and they seek assistance before an upcoming test.
  • Another participant suggests using the alternating series test as a potential method for analysis.
  • A different participant points out that as n approaches infinity, the absolute value of the terms approaches 2, implying that the series cannot converge regardless of its alternating nature.
  • One participant mentions that the series is bounded and does not diverge to positive or negative infinity, but asserts that it does not converge to a well-defined limit point.
  • Another participant emphasizes that if the terms do not approach zero, the series cannot converge, referencing a fundamental property of series.

Areas of Agreement / Disagreement

Participants express differing views on the convergence of the series, with some arguing it cannot converge due to the limiting behavior of the terms, while others propose that the alternating series test may still be relevant. The discussion remains unresolved regarding the series' convergence status.

Contextual Notes

Participants note limitations in their analysis, including the applicability of various convergence tests and the behavior of the series' terms as n approaches infinity.

Who May Find This Useful

Students preparing for tests on series convergence, particularly those studying alternating series and convergence tests in calculus.

SigurRos
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I apologize right now for the fact that I have no idea how to use LaTeX

I can't figure out if the following alternating series is convergent or not:

Sum(((-1)^(n-1)) * ((2n+1)/(n+2))) from 1 to infinity

the root test is not applicable, A(n+1)>An, and the ratio test gives me Limit=1, so I have no comclusive evidence either way. Even Maple 10 couldn't give me an answer.
I have a test tomorrow. HELP!
 
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Did you try the alternating series test?
 
Just take a look at the limiting terms in that series. As n goes to infinity the absolute value of the terms goes to two, so alternating or not there is no way it can converge.
 
BYW. I'm petty sure you can show that the above series is bounded, that is that it doesn't creep off to +/- infinity, but it definitely doesn't converge to a well defined limit point.
 
You are aware, are you not, that is an does not go to zero, then the series[itex]\Sigma a_n[/itex] cannot converge? That's normally the very first "series" property you learn!
 

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