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

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SUMMARY

The discussion focuses on using the reduction of order method to find a second linearly independent solution, y2(x), for the ordinary differential equation (ODE) given by x^2y'' - x(x+2)y' + (x+2)y = 0, with a known solution y1(x) = x. The user attempts to express y2 as v(x)y1(x) and calculates its derivatives, leading to a substitution into the ODE. The resulting equation simplifies to x^3(v'' - v') = 0, indicating that v' must be constant, which the user initially overlooks. The discussion emphasizes the importance of careful notation to avoid confusion in the solution process.

PREREQUISITES
  • Understanding of ordinary differential equations (ODEs)
  • Familiarity with the reduction of order method
  • Knowledge of derivatives and their applications in solving ODEs
  • Basic algebraic manipulation skills
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Students and educators in mathematics, particularly those studying differential equations, as well as anyone seeking to deepen their understanding of the reduction of order method in ODEs.

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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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You have two terms left over: ##x^3 (v'' - v')=0##.
 
Oh, wow. I overlooked the same thing three times...

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

Thanks.
 

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