Using the limit comparison test

In summary, the conversation discusses using the limit comparison test to determine convergence of a series. The person asking the question is confused about which term to divide for the test, but eventually figures it out. They also ask if the test would still prove convergence if the limit evaluates to infinity, to which the response is that the test only applies if the limit exists finitely and is not zero.
  • #1
hivesaeed4
217
0
I'm given the following:
3/(n(2^(n-1)))
I have to determine convergence using the limit comparison test. I've proved its convergent using the ratio test but am struggling with which term do I divide the above for the limit comparison test. Help?
 
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  • #2
Don't bother replying. I figured it out.
 
  • #3
I have just one question. Suppose the limit comparison test evaluates to infinity. Would it still prove convergence?
 
  • #4
hivesaeed4 said:
I have just one question. Suppose the limit comparison test evaluates to infinity. Would it still prove convergence?


Either you're asking something else or you're confusing the limit comparison test: this test tells you that if the limit of the quotient of two positive sequences exists finitely and is NOT zero, then the series whose general term is one of the seq's converges iff the series whose general term is the other seq. converges...so what's your question?

DonAntonio
 
  • #5
Sorry. I should have been clearer. The question was if the limit comparison test evaluates to infinity and we used a series whose general term was known to be convergent then the series whose general term's convergence we have to determine, is it also convergent. You answered that question by stating the finite part. Thanks
 

What is the limit comparison test?

The limit comparison test is a method used in calculus to determine the convergence or divergence of a series. It involves comparing the given series to a known series with known convergence properties.

How do you use the limit comparison test?

To use the limit comparison test, you first need to find a known series that is either known to converge or diverge. Then, you take the limit of the quotient of the terms of the given series and the known series. If the limit is a finite positive number, then the given series will have the same convergence properties as the known series.

What are the conditions for using the limit comparison test?

The limit comparison test can only be used on series with positive terms. Additionally, both series must have the same number of terms and the terms must be non-zero. Lastly, the known series must have known convergence properties.

What is the difference between the limit comparison test and the direct comparison test?

The direct comparison test involves directly comparing the given series to a known series, while the limit comparison test involves taking the limit of the quotient of the terms of the given series and the known series. Additionally, the direct comparison test can only be used when both series have positive terms, while the limit comparison test can also be used when one or both series have alternating terms.

Can the limit comparison test be used to determine absolute or conditional convergence?

Yes, the limit comparison test can be used to determine both absolute and conditional convergence. If the known series is absolutely convergent, then the given series will also be absolutely convergent. If the known series is conditionally convergent, then the given series may be either conditionally convergent or divergent.

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