Does This Alternating Series Diverge?

Leibniz's rule.In summary, the given series does not converge absolutely and cannot be analyzed using the theorems in the alternating sequences section. Two possible approaches to analyze it are finding an asymptotic approximation and using Leibniz's rule, or finding another series with terms that are greater than or equal to the terms in the given series and using Leibniz's rule again.
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Homework Statement


[tex]\sum_{n=2}^{\infty} \frac{(-1)^n}{\sqrt{n} + (-1)^n}[/tex]

Homework Equations


This is in the section covering alternating sequences. Leibniz's rule, conditional/absolute convergence, Dirichlet's test, and Abel's tests were all covered.

The Attempt at a Solution



I don't know what to apply here, it seems like none of the tests I have learned are applicable. Most of the theorems in this section covered sufficient conditions for convergence, which I can't turn back on themselves RAA to prove that this diverges. Obviously the series does not absolutely converge, and the even terms are greater in absolute value than the odd terms, so it will keep increasing, however I think there's a problem with approaching it this way since it is essentially grouping terms of the infinite sequence within parenthesis, which is not strictly allowed.
 
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  • #2
I think you can try two ways:
1) since you are interested in its behaviour when n is great, you can find an asymptotic approximation and then analyse it with Leibniz's rule;
or
2) you can find a series [itex]\sum b_n[/itex] such that [itex]b_n\geq a_n[/itex] (work on the denominator, trying to eliminate (-1)^n )
 

Related to Does This Alternating Series Diverge?

1. What is a "Prove series divergence"?

A "prove series divergence" is a mathematical concept used to determine whether an infinite series (a sum of infinitely many terms) diverges (increases without bound) or converges (approaches a finite limit).

2. How is "Prove series divergence" different from "Prove series convergence"?

"Prove series divergence" and "Prove series convergence" are opposite concepts. While "Prove series divergence" is used to show that a series increases without bound, "Prove series convergence" is used to show that a series approaches a finite limit.

3. What is the process for proving series divergence?

The process for proving series divergence involves using a test, such as the Divergence Test or the Integral Test, to show that the series does not converge. This can involve evaluating the limit of the series or comparing it to a known divergent series.

4. Why is it important to prove series divergence?

Proving series divergence is important because it allows us to determine whether an infinite series has a meaningful sum or not. If a series is proven to diverge, it means that the sum of its terms cannot be determined and the series has no finite value.

5. Can a series both converge and diverge?

No, a series can only either converge or diverge. It cannot do both. If a series is proven to converge, it means that the sum of its terms approaches a finite limit. If a series is proven to diverge, it means that the sum of its terms increases without bound.

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