Does This Sequence Converge to 2?

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Homework Help Overview

The discussion revolves around the convergence of a sequence defined by the limit of the expression \(\frac{2n}{n+1}\) as \(n\) approaches infinity. Participants are examining the validity of a limit proof and the underlying principles involved in establishing convergence.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to use the definition of a limit to prove convergence, while others question the clarity of certain expressions and the existence of specific values needed for the proof. There is also a discussion about the relevance of the Archimedean property and the approach to guessing limits when not explicitly provided.

Discussion Status

The discussion is active, with participants providing feedback on the original proof attempt and raising questions about the assumptions made. Some guidance has been offered regarding the importance of mentioning the Archimedean property, and there is an exploration of how to approach limits without prior knowledge of their values.

Contextual Notes

Participants are navigating potential typographical errors in mathematical expressions and discussing the implications of the Archimedean property in the context of limit proofs. There is an acknowledgment of the need for clarity in definitions and assumptions related to the problem.

Punkyc7
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use the definition of a sequence to establish the limit
lim([itex]\frac{2n}{n+1}[/itex])=2 Let [itex]\epsilon[/itex]>0, then |[itex]\frac{2n}{n+1}[/itex]-2| <[itex]\epsilon[/itex]. Next we have that | [itex]\frac{2n-2n+-2}{n+1}[/itex]|= |[itex]\frac{-2}{n+1}[/itex]| <[itex]\frac{2}{n}[/itex]. So [itex]\exists[/itex] k[itex]\in[/itex][itex]N[/itex] such that [itex]\frac{2}{k}[/itex]<[itex]\epsilon[/itex]. When n[itex]\geq[/itex]k, we have [itex]\frac{2}{n}[/itex] < [itex]\frac{2}{k}[/itex] <[itex]\epsilon[/itex]. Therefore the limit is 2. BLOCKIs this the right way to do a limit proof?
 
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Looks good. Some remarks:

Punkyc7 said:
| [itex]\frac{2n-2n+-2}{n+1}[/itex]|

2n+-2 is not something one writes. You'll have to write 2n+(-2) or simply 2n-2. I think you've just made a typo, but I wanted to make sure.

So [itex]\exists[/itex] k[itex]\in[/itex][itex]N[/itex] such that [itex]\frac{2}{k}[/itex]<[itex]\epsilon[/itex].

Why does such a k exist?
 
The Archimedean property right, is that something I should mention? Another question if we weren't given what the limit is equal to do you just make a guess and see if it right?
 
Punkyc7 said:
The Archimedean property right, is that something I should mention?

Yes, you should certainly mention that!

Another question if we weren't given what the limit is equal to do you just make a guess and see if it right?

Yes, you need to make an educated guess by looking at the graph or perhaps by using properties of the limit. But I'm sure you will see some easy ways to calculate limits soon.
 

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