How can I solve this ODE using Bernoulli equation with respect to x?

  • Thread starter AdrianZ
  • Start date
  • Tags
    Ode
In summary: Ce^{y^2/x}=-2/xe^{y^2/x}=-2CxIn summary, the given equation is a Bernoulli differential equation which can be solved by rewriting it in terms of a new variable u and using the integrating factor μ=e^(2y^2/x). The final solution is given by e^(y^2/x)=-2Cx.
  • #1
AdrianZ
319
0

Homework Statement


[tex]2xy'(x-y^2)+y^3=0[/tex]

Homework Equations





The Attempt at a Solution


What kind of an equation is that? I first thought that might be a Bernoulli differential equation with respect to x but I failed to convert it that form. I also checked if the equation could have single variable integrating factors but the answer is negative. How can I solve it?
 
Physics news on Phys.org
  • #2
I would approach it parametrically:

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

so:

[tex]\frac{dy}{dt}=-y^3[/tex]

[tex]\frac{dx}{dt}=2x(x-y^2)[/tex]

Note the first is de-coupled so solve that one and substitute it into the second one. Maybe though there is something I'm missing and would allow an easier approach.
 
  • #3
Thanks for your help jackmell but I already solved it as a Bernoulli equation with respect to x. I'll write down my answer so that it might be useful for someone else.
[tex]2xy^' (x-y^2 )+y^3=0[/tex]
[tex]2x(x-y^2 )+y^3 x^'=0[/tex]
[tex]x^'+(2x^2-2xy^2)/y^3 =0[/tex]
[tex]x^'+(-2/y)x=(-2/y^3 ) x^2[/tex]

so it's a Bernoulli equation and can be solved easily.
[tex]-x^{-2}+(2/y) x^{-1}=(2/y^3 )[/tex]
[tex]u=x^{-1}:du/dx=-x^{-2}[/tex]
[tex]{du/dx} {dx/dy}+(2/y)u=(2/y^3 )[/tex]
[tex]du/dy+(2/y)u=(2/y^3 )[/tex]
[tex]μ=e^{∫2dy/y}=y^2[/tex]
[tex]uy^2=∫y^2 (2/y^3 )dy[/tex]
[tex]Ce^{y^2/x}=y^2[/tex]
 

1. How do I identify the type of ODE?

There are three main types of ODEs: ordinary differential equations (ODEs), partial differential equations (PDEs), and integro-differential equations (IDEs). To identify the type of ODE, you need to look at the highest order derivative in the equation. If the highest order derivative is with respect to a single independent variable, then it is an ODE. If the highest order derivative is with respect to multiple independent variables, then it is a PDE. If the equation involves both derivatives and integrals, then it is an IDE.

2. What are the general steps for solving an ODE?

The general steps for solving an ODE are: 1) Identify the type of ODE, 2) Rewrite the ODE in standard form, if necessary, 3) Determine the order of the ODE, 4) Find the general solution by solving the ODE, 5) Apply any initial or boundary conditions to find the particular solution, and 6) Check your solution by plugging it back into the original equation.

3. What techniques can I use to solve an ODE?

There are several techniques that can be used to solve an ODE, including separation of variables, integrating factor, variation of parameters, and power series. The appropriate technique to use depends on the type and complexity of the ODE.

4. How do I handle initial or boundary conditions?

Initial or boundary conditions are used to find the particular solution of an ODE. They can be applied by substituting the given values into the general solution of the ODE. If the ODE is a higher order equation, multiple initial or boundary conditions may be needed to fully determine the particular solution.

5. What if I cannot find an analytic solution to the ODE?

If it is not possible to find an analytic solution to an ODE, numerical methods can be used to approximate the solution. These methods involve breaking the interval of interest into smaller subintervals and performing calculations at specific points within those subintervals. Examples of numerical methods include Euler's method, Runge-Kutta method, and finite difference method.

Similar threads

Replies
4
Views
501
  • Calculus and Beyond Homework Help
Replies
2
Views
1K
  • Calculus and Beyond Homework Help
Replies
3
Views
333
  • Calculus and Beyond Homework Help
Replies
7
Views
688
  • Calculus and Beyond Homework Help
Replies
5
Views
1K
Replies
5
Views
1K
  • Calculus and Beyond Homework Help
Replies
10
Views
476
  • Calculus and Beyond Homework Help
Replies
3
Views
571
Replies
7
Views
523
  • Calculus and Beyond Homework Help
Replies
33
Views
3K
Back
Top