Finding a Second Linear Solution using Reduction of Order Method for ODEs

In summary, the conversation discusses using the method of reduction of order to find another linear solution for a given ODE. The attempt at a solution involves finding the second solution y2(x) in the form of v(x)y1(x) and using substitution to simplify the equation. Eventually, the solution is found to be x^3 (v'' - v')=0.
  • #1
Mangoes
96
1

Homework Statement



Use the method of reduction of order to find another independently linear solution y2(x) when given one solution.

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

[tex] y_1(x) = x [/tex]

The Attempt at a Solution



Hopefully y2(x) will take the form of v(x)y1(x) or I have no idea how to solve the ODE. I start by finding y'2(x) and y''2(x).

[tex] y_2 = vx [/tex]
[tex] y'_2= v + xv' [/tex]
[tex] y''_2 = v' + v' + xv'' = 2v' + xv'' [/tex]

I substitute the above into the equation:

[tex] x^2(2v' + xv'') - x(x+2)(v + xv') + (x+2)vx = 0 [/tex]

[tex] 2x^2v' + x^3v'' - x^2v - x^3v' - 2xv - 2x^2v' + x^2v + 2xv = 0 [/tex]

And this is where I've gotten to. Everything cancels out and I can't see how I'll find my v...
 
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  • #2
You have two terms left over: ##x^3 (v'' - v')=0##.
 
  • #3
Oh, wow. I overlooked the same thing three times...

Might be worth switching notation to avoid this from happening again.

Thanks.
 

FAQ: Finding a Second Linear Solution using Reduction of Order Method for ODEs

What is the reduction of order of an ODE?

The reduction of order of an ODE, or ordinary differential equation, is a method used to solve higher-order ODEs by converting them into a system of first-order ODEs.

Why is reduction of order important in solving ODEs?

Reduction of order is important because it allows us to solve higher-order ODEs using techniques that are applicable to first-order ODEs. This makes the problem easier to solve and more intuitive to understand.

What are the steps involved in reducing the order of an ODE?

The steps involved in reducing the order of an ODE are as follows:

  1. Identify the highest derivative in the ODE
  2. Substitute a new variable for this derivative
  3. Rewrite the ODE in terms of the new variable and its derivatives
  4. Solve the resulting first-order ODE using standard techniques
  5. Substitute the original variable back into the solution to obtain the final solution

What types of ODEs can be solved using reduction of order?

Reduction of order can be used to solve any ODE of any order, as long as it is linear and homogeneous. This means that the ODE can be written in the form of a linear combination of the dependent variable and its derivatives, with coefficients that are functions of the independent variable only.

Are there any limitations to using reduction of order to solve ODEs?

Yes, there are some limitations to using reduction of order. This method can only be used for linear and homogeneous ODEs, which means it cannot be applied to non-linear or non-homogeneous ODEs. Additionally, it may not be applicable to ODEs with singular points or boundary conditions that are difficult to satisfy.

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