Analysis Applying Combination Rules

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Discussion Overview

The discussion centers around the analysis of two mathematical statements involving sequences and their limits, specifically focusing on the implications of the quotient and sum combination rules in the context of limits. Participants are exploring whether certain conditions lead to specific conclusions regarding the convergence of sequences.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Homework-related, Mathematical reasoning

Main Points Raised

  • One participant presents two statements for evaluation: (a) If bn ≠ 0 and an/bn → 1, then an - bn → 0; (b) If bn ≠ 0, bn is bounded, and an/bn → 1, then an - bn → 0.
  • Another participant expresses uncertainty about the truth of the statements and seeks assistance in proving or disproving them.
  • A participant suggests that the second statement is true, arguing that since bn is bounded and an/bn approaches 1, it follows that |an - bn| approaches 0.
  • A different participant confirms the reasoning for the second statement and proposes a counterexample for the first statement, suggesting an = n + 1 and bn = n as a potential case to consider.

Areas of Agreement / Disagreement

Participants express differing views on the truth of the first statement, with one participant believing it to be false while another has not yet reached a conclusion. There is agreement on the validity of the second statement, but the first remains contested.

Contextual Notes

Participants have not fully resolved the implications of the first statement, and there is ongoing exploration of the conditions under which the statements hold true. The discussion reflects uncertainty regarding the proofs and counterexamples needed to substantiate claims.

Who May Find This Useful

Students or individuals interested in mathematical analysis, particularly in the study of limits and convergence of sequences, may find this discussion beneficial.

nlews
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True or False, with a proof or counterexample.

a) If bn ≠ 0 and an/bn →1, then an-bn → 0
b) If bn ≠ 0, bn is bounded and an/bn → 1 then an-bn → 0

At the moment I cannot even see which is false so I am struggling with this question. I think the proof will require use of the quotient combination rule and the sum combination rule but I cannot see where to start! Any help would be appreciated!
 
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Do you at least have a guess?
 
Yes! Sorry I am new so wasnt sure how this all worked!

Basically I think the first is false and the second true!
I think this because for the second one,
if i use the fact that an/bn →1
I can say that
|an-bn| = bn |an/bn -1| → 0 because bn is bounded.

I think this works?

I can't really prove that the first is false, but I am working on that one at the moment! Any help would be great!
 
Yes. That absolutely works for the second. For the first consider a_n = n + 1 and b_n = n.
 

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