How can I simplify these ODEs?

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Homework Help Overview

The discussion revolves around simplifying two ordinary differential equations (ODEs). The first equation is given as \( y'=\frac{y^{2}+xy^{2}}{x^{2}y-x^{2}} \) and the second as \( xyy'=\frac{x^{2}+1}{y+1} \). Participants are exploring methods to express these equations in simpler forms.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to separate variables and integrate both equations but struggles to express the results in a simpler or explicit function form. Some participants discuss the nature of implicit versus explicit solutions and the acceptance of implicit solutions in the context of differential equations.

Discussion Status

Participants are engaged in clarifying the distinction between implicit and explicit solutions. Guidance has been offered regarding the acceptance of implicit solutions and the handling of constants of integration. There is an ongoing exploration of understanding these concepts without a clear consensus on the best approach to simplify the equations.

Contextual Notes

There is a noted uncertainty regarding the definitions of implicit and explicit forms, which may affect the participants' understanding of their solutions. The original poster expresses confusion about the implications of their results.

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Homework Statement


the first one
y'=[itex]\frac{y^{2}+xy^{2}}{x^{2}y-x^{2}}[/itex]

the second one
xyy'=[itex]\frac{x^{2}+1}{y+1}[/itex]

Homework Equations





The Attempt at a Solution


i separated x and y variable then integrate both of them

in the first one
∫[itex]\frac{y-1}{y^{2}}[/itex]dy=∫[itex]\frac{1+x}{x^{2}}[/itex]dx

ln|y|+[itex]\frac{1}{y}[/itex]+C=- [itex]\frac{1}{x}[/itex]+ln|x|+C

and the second one
∫y(y+1)dy = ∫[itex]\frac{x^{2}+1}{x}[/itex]dx

[itex]\frac{y^{3}}{3}[/itex]+[itex]\frac{y^{2}}{2}[/itex]+C=[itex]\frac{x^{2}}{2}[/itex]+ln|x|+C

but i can't change both of them into f(x) form or any simpler form
 
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It is rare that you will find a differential equation with a solution that can be written as an explicit function. Implicit solutions, the equations relating x and y that you found, are usually accepted as finding a solution to a differential equation as well. As long as there are no derivatives in your final equation, and you specify the domain of the implicit function y that is defined by your equation, where it satisfies the original differential equation, you have found a solution.
Note, however, that you do not need two constants of integration: you may condense them into a single constant: C1 - C2 = C.
 
slider142 said:
It is rare that you will find a differential equation with a solution that can be written as an explicit function. Implicit solutions, the equations relating x and y that you found, are usually accepted as finding a solution to a differential equation as well. As long as there are no derivatives in your final equation, and you specify the domain of the implicit function y that is defined by your equation, where it satisfies the original differential equation, you have found a solution.
Note, however, that you do not need two constants of integration: you may condense them into a single constant: C1 - C2 = C.

i see, i just don't really understand the difference between implicit and explicit form, so the thing i just solve is the implicit form.. thanks for answering
 
The only thing to "understand" about "implicit" and "explicit" form is that the explicit form is always "y= some expression in x only" and the implicit form isn't!
 

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