Does This Sequence Converge to 2?

In summary, the limit definition was used to prove that the limit of the sequence \frac{2n}{n+1} is equal to 2. The Archimedean property was mentioned to explain the existence of a suitable k value. If the limit is not given, an educated guess can be made using properties of the limit or by analyzing the graph.
  • #1
Punkyc7
420
0
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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  • #2
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?
 
  • #3
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?
 
  • #4
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.
 

FAQ: Does This Sequence Converge to 2?

What is the definition of the limit of a sequence?

The limit of a sequence is a fixed value that the terms of the sequence approach as the number of terms increases to infinity. It is denoted by lim n→∞ an, where "an" represents the nth term of the sequence.

How is the limit of a sequence calculated?

The limit of a sequence can be calculated by finding the pattern or trend in the sequence and observing the behavior of the terms as "n" approaches infinity. This can be done using various mathematical techniques such as the squeeze theorem, the ratio test, or the root test.

What does it mean if the limit of a sequence is 2?

If the limit of a sequence is 2, it means that as the number of terms in the sequence increases, the terms approach the value of 2. This does not necessarily mean that the value of the terms will ever be exactly 2, but they will get closer and closer to it as "n" approaches infinity.

Can the limit of a sequence be any number?

No, the limit of a sequence can only be a single fixed value. It cannot be a range of numbers or an infinite number of numbers. However, it is possible for the limit to be undefined or infinite, depending on the behavior of the terms in the sequence.

How is the limit of a sequence used in real-world applications?

The concept of the limit of a sequence is used in many real-world applications, such as predicting stock prices, analyzing data trends, and in engineering and physics to understand the behavior of systems. It is also a fundamental concept in calculus and is used to calculate derivatives and integrals.

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