Solving a homogeneous first-order ordinary differential eqn

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Homework Help Overview

The problem involves solving a first-order ordinary differential equation of the form dy/dx = (x + 4y)^2, which is being approached as a homogeneous equation.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts a substitution method with y = ux to achieve a separable form but encounters difficulties. Another participant suggests a different substitution, u = x + 4y. A third participant questions the assumption of homogeneity in the differential equation.

Discussion Status

The discussion includes various attempts to clarify the nature of the equation and the appropriateness of the substitutions being used. Some participants are exploring different interpretations of the problem, and there is an indication that guidance has been provided regarding the assumptions made.

Contextual Notes

There is a noted confusion regarding the definition of homogeneity in the context of the differential equation, which may affect the approach taken by the original poster.

Aceix
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Homework Statement


dy/dx = (x+4y)2

Homework Equations

The Attempt at a Solution


I substitute y=ux, where u is a function of x, and I'm not a ble to solve. My intention was to arrive at a seperable form, but I'm not achieving it.[/B]
 
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Try the substitution u=x+4y.
 
@Aceix Your problem is assuming your DE is homogeneous. Homogeneous in this sense means ##f(tx,ty) = f(x,y)##. That does't work for ##f(x,y)=(x-4y)^2##.
 
Thanks a lot! I've got it now.
 

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