Testing Divergence: Alternating Series

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    Divergence Testing
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Discussion Overview

The discussion centers around the application of the Test for Divergence to alternating series, specifically whether the limit of the terms in such series can indicate divergence. Participants explore the implications of the divergence test in the context of a specific example involving the series sum of ((-1)^n)/n.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant questions if the Test for Divergence can be applied to alternating series, suggesting that the limit of the terms does not exist and may imply divergence.
  • Another participant asserts that the Test for Divergence indicates divergence.
  • A third participant presents a counterexample with the series sum of ((-1)^n)/n, arguing that the divergence test suggests divergence due to the alternating nature of the terms, despite the series actually converging according to the alternating series test.
  • A subsequent reply clarifies that the limit of the terms in the series ((-1)^n)/n approaches zero, indicating that the divergence test does not provide conclusive information about the series' convergence.

Areas of Agreement / Disagreement

Participants express disagreement regarding the application of the Test for Divergence to alternating series, with some asserting it indicates divergence while others provide counterexamples that suggest convergence.

Contextual Notes

The discussion highlights the limitations of the divergence test when applied to alternating series, particularly regarding the behavior of limits and the conditions under which the test is informative.

Sahara
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Can the Test for Divergence (limit of an->infinity not equal to zero) be used on an alternating series?
For example, if a series has a (-1)^n term. Can we assume that since the limit of that term does not exist, then the series is automatically diverging?
 
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Yes.
 
Ok,
but what about the sum of ((-1)^n)/n? Doesn't the divergence test say that this sum diverges because of the alternating 1, while the series converges with the alternating series test..
 
No, because

<br /> \lim_{n \to \infty} \frac{(-1)^n}{n} = 0<br />

so that test doesn't provide any information.
 
oh alright! thank you
 

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