Limit of a rational function with a square-rooted expression in numerator.

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Discussion Overview

The discussion revolves around evaluating the limit of a rational function involving a square-rooted expression in the numerator as x approaches 0. Participants explore various methods to solve the limit, including rationalization and l'Hôpital's rule, while expressing challenges encountered during the evaluation process.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents the limit expression and expresses difficulty in reaching the limit of 1/4.
  • Another participant inquires about the methods attempted so far, prompting further exploration.
  • A participant mentions trying to divide out by (x+4)1/2 and x, leading to complications that result in infinity.
  • There is a suggestion to use l'Hôpital's rule, with a participant confirming familiarity with it but initially questioning its applicability.
  • Another participant asserts that both rationalizing the numerator and using l'Hôpital's rule should work, noting that rationalizing is good practice.
  • There is a clarification about the use of l'Hôpital's rule for indeterminate forms, specifically 0/0 or ±∞/∞, which applies to the current limit scenario.
  • A participant acknowledges a mistake in not recognizing the indeterminate form and expresses gratitude for the assistance.

Areas of Agreement / Disagreement

Participants express differing views on the methods to evaluate the limit, with some favoring rationalization and others advocating for l'Hôpital's rule. The discussion remains unresolved regarding the preferred approach, as participants explore multiple methods without consensus.

Contextual Notes

Participants mention the conditions under which l'Hôpital's rule can be applied, indicating that the limit presents an indeterminate form. There are also references to the challenges of manipulating the expressions involved, which may affect the clarity of the evaluation process.

MurdocJensen
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lim as x -> 0, [(x+4)1/2-2]/x

That's the limit I want to evaluate. I keep running into problems getting to the real limit (1/4).
You don't have to give me the answer, but let me know if I'm missing something simple. Or you can just give me a hint.
 
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What have you tried so far?
 
So far I have tried dividing out by (x+4)1/2. This still gives me an x in the denominator that yields infinity when x->0.

I have also tried dividing out by x, but this gives me fractions in the numerator that, again, give me infiinity.
 
Have you learned l'hopital's rule yet?
 
Yea, but I was able to get the answer by just rationalizing the numerator. I'm going to try l'Hospital now.

EDIT: I thought we only use l'Hospital's rule for lmits that are 0/0 or inf/inf.
 
Both methods should work. l'hopital's rule will probably be easier, but rationalizing the numerator is good practice.
 
But aren't we using l'Hospital's rule for indeterminate forms?
 
MurdocJensen said:
But aren't we using l'Hospital's rule for indeterminate forms?

You can use l'hopital's rule for 0/0 or +-inf/inf (which in this case you get 0/0). I was just saying there's more than one way of getting the right answer.
 
gb7: Yea, I'm an idiot for not noticing that. Thanks for the help!
 

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