What is the limit of (2n+1)/(3n+7) as n approaches infinity?

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Discussion Overview

The discussion revolves around finding the limit of the expression (2n+1)/(3n+7) as n approaches infinity, with a focus on proving the limit using a formal definition. Participants explore different approaches and clarify concepts related to limits in calculus.

Discussion Character

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

Main Points Raised

  • One participant presents the expression an = (2n+1)/(3n+7) and requests help in proving that the limit approaches 2/3 directly from the definition.
  • Another participant questions the definition of the limit statement "lim((2n+1)/(3n+7)) = 2/3," suggesting that understanding the definition is a crucial first step.
  • A participant proposes a manipulation of the expression to analyze its behavior as n increases, rewriting it as [(2n)(1+1/2n)]/[(3n)(1+7/3n)] and inquires about the behavior of the terms 1/2n and 7/3n as n grows larger.
  • A similar point is reiterated by another participant, emphasizing that while their approach simplifies finding the limit, it does not fulfill the requirement of proving it from the definition.

Areas of Agreement / Disagreement

Participants express differing views on the best approach to prove the limit, with some focusing on the definition and others on algebraic manipulation. No consensus is reached on a single method or proof.

Contextual Notes

Participants have not fully defined the formal definition of limits, and there are unresolved aspects regarding the steps needed to prove the limit rigorously.

Who May Find This Useful

Students and individuals interested in calculus, particularly those seeking to understand limits and formal proofs in mathematical analysis.

asset101
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let an = [tex]\frac{(2n+1)}{(3n+7)}[/tex]. Prove direct from definition that an[tex]\rightarrow2/3[/tex].

Any help would be appreciated.
Cheers
 
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ok … first step in a question like this is …

what is the definition of the statement "lim((2n+ 1)/(3n+7)) = 2/3"? :smile:
 
Here's an idea... as long as n isn't zero, the following two things are the same:

(2n+1)/(3n+7) = [(2n)(1+1/2n)]/[(3n)(1+7/3n)]

What happens as the n's get bigger and bigger to the terms 1/2n and 7/3n?
 
AUMathTutor said:
Here's an idea... as long as n isn't zero, the following two things are the same:

(2n+1)/(3n+7) = [(2n)(1+1/2n)]/[(3n)(1+7/3n)]

What happens as the n's get bigger and bigger to the terms 1/2n and 7/3n?
That's the simplest way of finding the limit but it doesn't "prove from the definition".
 

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