Is this solution to a limit equation correct?

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Homework Help Overview

The discussion revolves around the evaluation of a limit equation involving the expression \(\lim _{(x,y)\to (\infty,0)} \frac{1}{(x-y)^{x}}\). Participants are examining the validity of different interpretations and the reasoning behind the original poster's conclusion that the limit equals 1.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster questions why their interpretation of the limit as 1 is considered incorrect, exploring the equivalence to forms like \(1 - \infty^{-\infty}\) and \(1 - \text{infinitesimal}\). Some participants assert that the limit approaches 0 instead, discussing the behavior of \((x-y)^{x}\) as \(x\) approaches infinity.

Discussion Status

Participants are actively engaging with the problem, with some providing insights into the nature of the limit and questioning the assumptions made by the original poster. There is no explicit consensus on the correct interpretation, but there is a productive exchange of ideas regarding the limit's behavior.

Contextual Notes

The original poster expresses uncertainty about their reasoning and seeks clarification on the logic behind their answer being deemed incorrect. There is an emphasis on the need for clearer mathematical expressions, as noted by one participant's suggestion to use LaTeX for posting equations.

nedfin
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Homework Statement
I ran into this equation online and an interested in why my answer might be wrong. What if anything is wrong with my logic.
Relevant Equations
1-(1/((x-y)^x))
lim(x,y) -> (inf,0)
Why is this not equivalent to

1 - inf^-inf,

Or 1 - infinitesimal ,

Or 1 ?

My answer was 1, which I told is incorrect.
 
Last edited:
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<br /> \lim _{(x,y)\to (\infty,0)} \frac{1}{(x-y)^{x}} = 0<br />
because ##(x-y)^x \to \infty ## as ##(x,y)\to (\infty,0)##. It is not equivalent to the first two items. ##\infty ^{-\infty}## is not a thing and neither is "infinitesimal". The initial limit is ##1## as you say.
 
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nuuskur said:
<br /> \lim _{(x,y)\to (\infty,0)} \frac{1}{(x-y)^{x}} = 0<br />
because ##(x-y)^x \to \infty ## as ##(x,y)\to (\infty,0)##. It is not equivalent to the first two items. ##\infty ^{-\infty}## is not a thing and neither is "infinitesimal". The initial limit is ##1## as you say.
Thanks
 
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nedfin said:
Homework Statement:: I ran into this equation online and an interested in why my answer might be wrong. What if anything is wrong with my logic.
Relevant Equations:: 1-(1/((x-y)^x))
lim(x,y) -> (inf,0)

Why is this not equivalent to

1 - inf^-inf,

Or 1 - infinitesimal ,

Or 1 ?

My answer was 1, which I told is incorrect.
Welcome to PF. :smile: I'm glad that @nuuskur was able to help you.

BTW, please consider learning LaTeX to post equations in discussion forums. You can find a "LaTeX Guide" link at the bottom of the Edit Window. It makes math equations *much* easier to read (as you can see by nuuskru's post). :smile:
 

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