In limits, how do you tell immediately if the only way to solve the

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    Limits
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Discussion Overview

The discussion revolves around understanding limits in mathematics, specifically how to determine when a problem can be solved by inspection versus when it requires rewriting the equation. Participants explore examples and concepts related to sequences approaching a limit.

Discussion Character

  • Conceptual clarification, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant questions how to identify when testing a limit by inspection is sufficient, citing examples like 0.99, 0.999, and 0.9999.
  • Another participant expresses a basic understanding of limits, suggesting that limits involve approaching a constant value.
  • A third participant agrees with the confusion expressed and seeks clarification on the initial question.
  • One participant argues that limits cannot be determined solely by testing terms, emphasizing the importance of identifying the general term of a sequence to prove convergence.
  • This participant also notes that while one might observe a pattern in a sequence, proving the limit requires rewriting the sequence in a specific mathematical form.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the concept of limits, with some agreeing on the need for a general term to prove limits, while others remain uncertain about the initial question and its implications.

Contextual Notes

There is an assumption that the pattern in the sequence continues, but this is not explicitly stated as a given. The discussion also highlights the potential for sequences to change rules, which complicates the determination of limits.

Deathfish
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In limits, how do you tell immediately if the only way to solve the problem is to test it out? What are some cases where rewrtiting the equation won't get results?

eg. 0.99, 0.999, 0.9999
 
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i didn't get you Mr. in limits we just approach a constant or a value closer than the closest possibility... this is the only concept of limits in my view...
 
Hi Deathfish!

Yes, I don't get you either. :confused:

(and welcome to PF, satyasaichand! :smile:)
 


If I am interpreting this correctly, strictly speaking you never can find a limit by "testing it out" (which I interpret to mean writing out "enough" terms to determine by inspection what it converges to). It is quite possible that the sequence is .99, .999, .9999 (1- .1^(n+1) is the general term) for the first, say, million terms then changes to some other rule entirely. You must be able to determine what the general term is.]

(Problems where you are given a finite sequence of numbers and expected to determine the general term are common in mathematics- the ability to recognise a pattern is an important skill in mathematics- but, strictly speaking, they should state that the pattern does not change.)


Assuming that the pattern in .99, .999, .9999, .99999, etc. continues then you can see that it is approaching 1 by 'looking at it', but if you want to prove that, you should rewrite it as [itex]1- .1^{n+1}[/itex]. Whether or not you can recognise a limit "by inspection" depends on how familiar you are with sequences. It is proving that limit that typically requires writing the general term in some specific form.
 

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