Solve First Order Homogeneous ODE | Constants a and b | Help Needed!

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In summary, the conversation is about solving a first order homogeneous ODE with the equation y'(x)-(a/x)y = b/(x(1+x)^2), where a and b are constants. The attempts so far have involved using an integrating factor x^(-a), but this led to a solution involving Gauss hyper-geometric functions. The conversation also discusses using parts to simplify the integral and comparing the solution to the one reported by Mathematica. The problem is part of a larger project and the individual is experiencing some difficulties with solving it.
  • #1
Konig
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Hi, need help solving a first order homogeneous ODE.

y'(x)-(a/x)y = b/(x(1+x)^2) Here a and b are some constants.

Need to solve this for y.

My attempts so far have been to use

img1.gif


But this means solving ∫ x^(-a)/(x(1+x)^2) dx which has solutions in terms of Gauss hyper-geometric functions,

http://en.wikipedia.org/wiki/Hypergeometric_function"

Which lead me to believe I'm going wrong somewhere...

Sorry for the maths format, I'm new to here and don't know how to insert LaTeX.

Thanks
 
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  • #2
What, he didn't give you an easy one huh? But isn't the integrating factor x^(-a) so that you get:

[tex]d(yx^{-a})=\frac{b}{x^{1+a}(1-x)^2}[/tex]

Now suppose all you had to do was:

[tex]\int \frac{b}{x^{1+a}(1-x)^2}dx[/tex]

Could you use parts say, one, two, three, four times, look at what's happening to the sequence, then come up with a general (infinite-term) expression for the solution that when you checked out the power-series expression for the Hypergeometric series solution reported by Mathematica, the series you get looks like it?
 
  • #3
thanks for the response Jackmell,

Am currently working on it, though keep making maths errors which are slowing me down.

I agree it would be a good idea to compare, thanks for the tip.

The problem is part of a project, so yea the problems not meant to be easy.
demoralising thing though is that I'm not sure i was supposed to take this long with it!

Konig
 

FAQ: Solve First Order Homogeneous ODE | Constants a and b | Help Needed!

What is a first order homogeneous ODE?

A first order homogeneous ODE (ordinary differential equation) is a mathematical equation that relates a function and its derivatives. In a first order homogeneous ODE, the function and its derivatives are of the same order, and the equation is set equal to zero.

How do I solve a first order homogeneous ODE?

To solve a first order homogeneous ODE, you can use the method of separation of variables. This involves rewriting the equation in a form where all the dependent and independent variables are on one side and the constants are on the other side. Then, you can integrate both sides to find the general solution.

What are the constants a and b in the first order homogeneous ODE?

The constants a and b represent the initial conditions of the differential equation. These values are typically given in the problem or can be determined by substituting the initial values of the dependent and independent variables into the general solution.

Can you give an example of solving a first order homogeneous ODE?

Sure, for example, let's consider the equation dy/dx = -2xy. To solve this, we can separate the variables and integrate both sides: dy/y = -2x dx. Integrating gives ln|y| = -x^2 + C. From the initial condition y(0) = 1, we can find C = 0. Therefore, the solution is y = e^(-x^2).

What are some applications of first order homogeneous ODEs?

First order homogeneous ODEs have many applications in physics, engineering, and other fields. For example, they can be used to model population growth, chemical reactions, and electrical circuits. They are also essential in solving higher order differential equations and in developing mathematical models for real-world systems.

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