Is the Cauchy Equation Still Homogeneous if X is a Non-zero Function of x?

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Discussion Overview

The discussion centers around the nature of the Cauchy homogeneous linear differential equation, particularly whether it remains homogeneous when the right side, denoted as X, is a non-zero function of x. The scope includes theoretical considerations of differential equations and the definitions of homogeneity.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant states that for the Cauchy equation to be homogeneous, the right side must equal zero, questioning how it can be considered homogeneous if X is a function of x.
  • Another participant asserts that the equation is not homogeneous and challenges the terminology used, suggesting that there may be confusion stemming from external sources.
  • A participant proposes a transformation of the equation to make the right side zero, implying that this could render the equation homogeneous.
  • Another participant agrees with the previous point but emphasizes that X is a function of x, suggesting that this transformation does not apply in the context of non-constant functions.
  • One participant acknowledges an assumption that X was constant, later correcting themselves to clarify that X is indeed a function of x and not a constant.
  • A participant reiterates that with X as a function of x, the equation cannot be considered homogeneous, and questions if it would still be non-homogeneous even if X were a constant.
  • A later reply confirms the assertion that the equation is not homogeneous, regardless of whether X is a constant or a function of x.

Areas of Agreement / Disagreement

Participants generally disagree on the classification of the equation as homogeneous or not, with some asserting it is not homogeneous due to the nature of X, while others explore the implications of transformations that could affect this classification. The discussion remains unresolved regarding the terminology and definitions used.

Contextual Notes

Participants express varying assumptions about the nature of X, with some initially treating it as a constant before clarifying that it is a function of x. The implications of these assumptions on the classification of the equation as homogeneous or not are not fully resolved.

iVenky
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The Cauchy homogeneous linear differential equation is given by

x^{n}\frac{d^{n}y}{dx^{n}} +k_{1} x^{n-1}\frac{d^{n-1}y}{dx^{n-1}} +...+k_{n}y=Xwhere X is a function of x and k_{1},k_{2}...,k_{n} are constants.

I thought for this equation to be homogeneous the right side should be 0. (i.e.) X=0.
But if X is a function of x then how can this be homogeneous?

Thanks a lot :)
 
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It isn't. Why do you call it "homogeneous"?

(Googling "Cauchy's homogeneous equation", I found a "youtube" tape calling this equation "homogeneous"- its just wrong! I suspect they started talking about a homogeneous equation and did not change the title when they generalized).
 
Last edited by a moderator:
Let y(x) = Y(x)+(X/kn) and the rigth side will be 0.
 
JJacquelin said:
Let y(x) = Y(x)+(X/kn) and the rigth side will be 0.

If I do things like that, I can make any equation homogeneous.

Don't forget that X is a function of 'x'.
 
You are assuming that X is a constant, aren't you?
 
Sorry, I was assuming that X was constant.
So, my answer is out of subject.
 
I have chosen that X to be a function of 'x' and it is not a constant

So I think it is not homogeneous.

For the record even if X is a constant it is still not homogeneous, isn't it?

thanks a lot :)
 
iVenky said:
I have chosen that X to be a function of 'x' and it is not a constant

So I think it is not homogeneous.

For the record even if X is a constant it is still not homogeneous, isn't it?

thanks a lot :)
Yes, that is correct.
 

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