Proving Limit Exists with Cauchy Criterion for {X_n}

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In summary, the conversation discusses the need to prove the limit of a sequence using Cauchy's criterion. The sequence in question is {X_n}=(10/1)(11/3)...(n+9/2n-1) and a link to the Cauchy criterion is provided. The conversation also touches on the importance of fixing N and picking p in relation to proving the limit, as well as defining Sn as the sum of the series from a1 to an.
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  • #2
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  • #3
Your N is not fixed; it should depend on [tex]\varepsilon[/tex] only.

What's s?
Why did you pick p = 1?
 
  • #4
mutton said:
Your N is not fixed; it should depend on [tex]\varepsilon[/tex] only.

What's s?
Why did you pick p = 1?

give me a reason y i can't pick p=1

and bout the Sn
Sn= sum of the series from a1 to an

.
 
  • #5
No one has to give you a reason why you can't pick p= 1. You are the one who is doing this. Please answer the question- why DID you pick p= 1?
 

1. What is the Cauchy Criterion for proving the existence of a limit in a sequence?

The Cauchy Criterion is a test used to determine whether a sequence has a limit. This criterion states that a sequence is convergent if and only if for any small positive number, there exists a point in the sequence where all subsequent terms are within that small distance from each other. This essentially means that if the terms in a sequence become arbitrarily close to each other as the sequence progresses, then the sequence has a limit.

2. How is the Cauchy Criterion used to prove that a limit exists in a sequence?

To prove that a limit exists in a sequence using the Cauchy Criterion, we first need to show that the sequence is Cauchy. This means that for any small positive number, there exists a point in the sequence where all subsequent terms are within that small distance from each other. Once we have established that the sequence is Cauchy, we can then use this information to prove that the sequence has a limit.

3. What is the importance of proving that a limit exists in a sequence?

Proving that a limit exists in a sequence is important because it allows us to make predictions about the behavior of the sequence as it approaches its limit. This can be especially useful in fields such as calculus and physics, where understanding the behavior of sequences and their limits is crucial in solving problems and making accurate predictions.

4. Can the Cauchy Criterion be used to prove that a sequence is not convergent?

Yes, the Cauchy Criterion can be used to prove that a sequence is not convergent. If a sequence fails the Cauchy Criterion, it means that there exists a small positive number for which there is no corresponding point in the sequence where all subsequent terms are within that small distance from each other. This indicates that the terms in the sequence do not become arbitrarily close to each other, and therefore the sequence does not have a limit.

5. Are there any other methods for proving the existence of a limit in a sequence?

Yes, there are other methods for proving the existence of a limit in a sequence, such as the Monotone Convergence Theorem and the Bolzano-Weierstrass Theorem. These theorems provide alternative criteria for determining whether a sequence has a limit and can be useful in different situations.

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