Homogeneous Differential Equations

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Discussion Overview

The discussion revolves around determining whether a specific differential equation is homogeneous. Participants explore the definition of homogeneity in the context of both linear and nonlinear differential equations, and some express uncertainty regarding the applicability of the concept to nonlinear cases.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant presents a differential equation and seeks clarification on its homogeneity, particularly due to the presence of second and first derivatives.
  • Another participant asserts that the equation is homogeneous because it lacks terms that do not involve y or its derivatives, emphasizing the importance of understanding definitions over examples.
  • A later reply confirms the equation's homogeneity while noting its nonlinearity and suggests that this complicates the solving process.
  • One participant questions the relevance of homogeneity for nonlinear differential equations, indicating a lack of a general definition for such cases.
  • Another participant suggests a method to determine homogeneity by checking if Y(x) = 0 is a solution.
  • One participant asserts that the equation discussed is not homogeneous, providing a mathematical reasoning based on specific variable relationships.
  • A separate participant attempts to introduce a new question regarding a different differential equation, which leads to a reminder about maintaining thread relevance.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of the concept of homogeneity to nonlinear differential equations. While some agree on the homogeneity of the original equation, others challenge the relevance of the term in this context. The discussion remains unresolved regarding the broader implications of homogeneity in nonlinear cases.

Contextual Notes

There is a lack of consensus on the definition of homogeneity as it applies to nonlinear differential equations, and some participants express uncertainty about the implications of nonlinearity on the concept.

nados29
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Hi,

I need some help in finding whether this differential equation is homogeneous or not.

3 (d^2 y / dx^2) + x (dy/dx)^2 = y^2

I know that for example,

x^2 dx + xy dy = 0 is homogeneous. But how can I deal with the equation that has (d^2 y / dx^2) and (dy/dx)^2 ?

Thanks
 
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Is your question just to determine if the equation is homogeneous or not? If so, the fact that the equation is non-linear is not relevant: yes it is homogeneous because it does not have any terms which do NOT involve y or one of its derivatives.
(That's the advantage of knowing the DEFINITION rather than just some examples.)

Of course, the fact that it is non-linear pretty much means being homogeneous doesn't make it any easier to solve!
 
Just to format it:

[tex]3 \frac{d^2y}{dx^2}+x(\frac{dy}{dx})^2-y^2=0[/tex]

Hummmmm . . .
 
Indeed, homogeneous but additionally nonlinear. Quite analytically insoluble, though.
 
The simplist way to answer the question of homogeneity is to ask:

Is Y(x) = 0 a solution?

If the answer is yes, then the equation is homogeneous.
 
Hrm, does it really make sense to ask if a nonlinear DE is homogenous? I don't have a general definition handy, and Mathworld only defines homogeneity for linear differential equations.
 
Probably Mathworld gives attempts to solve it,too...Is a nonlinear algebraic system either homogenous or nonhomogenous...?:bugeye:

Daniel.
 
Hey i need some help finding the general solution of

ydy= (-x+ √(x^2 + y^2))dx

by using the substitution y= vx and then the substitution u^2= 1 + v^2

It would be great if someone could help.
 
Do not, do not, do not "hijack" someone else's thread for a new question. It's very easy to start a thread of your own!

In fact, I'm going to do that for you.
 
  • #10
your equation is not homogeneous:
It follows from k-2m=2k-m=2k, so k=0, m=0
 
  • #11
The original thread was resolved 30 months ago, or 32 months ago this month. :biggrin:

Halls of Ivy is correct. A new thread is appropriate for a new problem.
 

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