Limit as x approaches 2 from the right

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Discussion Overview

The discussion centers around evaluating the limit of the expression \(\lim_{x \rightarrow 2^+} \sqrt{x-2} \left( \frac{1}{x} - \frac{1}{2} \right)\). Participants explore the challenges in computing this limit, particularly focusing on the behavior of the expression as \(x\) approaches 2 from the right.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in taking the limit and seeks assistance.
  • Another suggests simplifying the denominator and finding a common denominator to resolve the limit.
  • A participant confirms the limit expression and inquires about the specific difficulties faced.
  • One participant simplifies the expression to \(\lim_{x \rightarrow 2^+} -\frac{\sqrt{x-2}}{2x}\) but still finds it unhelpful.
  • Concerns are raised about obtaining a real number when substituting \(x = 2^+\).
  • Another participant argues that substituting \(x = 2\) yields a real number, indicating no domain issues with \(\sqrt{x-2}\) for \(x \in [2, \infty)\).
  • A later reply mentions using Mathematica to compute the limit, which returns 0.
  • One participant mistakenly considers a different limit that could present more complexity.
  • There is a suggestion to apply L'Hôpital's rule, though another participant questions its necessity for the original limit.
  • Disagreement arises regarding whether the limit is zero or if there is an indeterminate form present.
  • Participants engage in a side discussion about the correct spelling of l'Hôpital's name and its historical context.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the value of the limit, with some asserting it is zero while others suggest there may be an indeterminate form. The discussion remains unresolved regarding the application of L'Hôpital's rule.

Contextual Notes

There are mentions of potential indeterminate forms and the necessity of L'Hôpital's rule, but these points are not fully resolved within the discussion.

huan.conchito
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[itex] Lim x->2^+ [Sqrt (x-2)] (1/x-1/2)[/itex]
Please help I am having trouble taking this limit
 
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Work on the denominator.Bring that expression to a common denominator and then see whether u can "fix" something with the big fraction's numerator...

Daniel.
 
Just to check, you want:

[tex] \lim_{x \rightarrow 2^+} \sqrt{x-2} \left( \frac{1}{x} - \frac{1}{2} \right)[/tex]

correct?

What is giving you trouble?
 
I simpliefied it to [itex]Lim x->2^+ -Sqrt[x-2]/ 2x[/itex], but that still doesn't help
 
yes, when i plug in [itex]2^+[/itex] i can't get a real number
 
I don't see the trouble... [itex]\sqrt{2-2}(\frac{1}{2} - \frac{1}{2})[/itex] is a perfectly real number... and there's no issues of domain, because [itex]\sqrt{x-2}[/itex] is defined and continuous on [itex]x \in [2, \infty)[/itex].
 
huan.conchito said:
yes, when i plug in [itex]2^+[/itex] i can't get a real number

Huan, I assume you've figured out how to specify a right-handed limit in Mathematica right?

[tex]Limit[\sqrt{x-2}(\frac{1}{x}-\frac{1}{2}),x\rightarrow 2,Direction\rightarrow -1][/tex]

This returns 0
 
Ooops,i was thinking about

[tex]\lim_{x\searrow 2}\frac{\sqrt{x-2}}{\frac{1}{x}-\frac{1}{2}}[/tex]

which would have been more interesting...

Daniel.
 
try to use L HOSPİTAL
 
  • #10
For what?It's not necessary for mine & it would be incorrect for theirs...

Daniel.

EDIT:And one more thing:It's Guillaume François Antoine,marquis de l'Hôpital.
 
Last edited:
  • #11
are you sure its zero ?
 
  • #12
there is o.o indefiniteness.u can use l hospital
not:full name is not important
 
  • #13
To his limit it's 0 times 0...No indefiniteness.:wink:

Oh,would you like to be called gursen...?

Daniel.
 
  • #14
what did you mean by saying 'Oh,would you like to be called gursen...?'
 
  • #15
U keep mispelling his name.I wonder if the French dude were still alive & were mis-speling your name,would you have liked it??

Daniel.
 
  • #16
lan mal i am from turkey
 
  • #17
Okay,i'm from Romania,our peoples go way back in the middle ages :wink:

But still,in modern French,l'Hôpital is l'Hôpital,okay?

Daniel.
 
  • #18
as i said name is not important.the important thing is the solution
 
  • #19
and however if i said hospital its hospital
 
  • #20
Funny,in the XVII-th century French,there was no circumflex accent in writing,so he'd spell his name l'Hospital ...:wink:

But the French language has evolved...

Daniel.
 

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