Stuck on the reduction of order step for solving this differential equation

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Homework Help Overview

The discussion revolves around solving a differential equation of the form (x - 1)y'' - xy' + y = sin(x) for x > 1, given that y_1(x) = e^x is a solution to the associated homogeneous equation. The focus is on the reduction of order technique to find a second solution.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the method of reduction of order, specifically the substitution of y_2 = v_2(x) * y_1 and the implications of terms involving v not dropping out as expected. Questions arise about whether the non-homogeneous term sin(x) should be ignored in the context of the reduction of order step.

Discussion Status

Some participants have provided guidance on the algebraic manipulation involved in the reduction of order, noting corrections to the form of v. However, there remains uncertainty about the next steps and the interpretation of the results obtained so far.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may limit the information they can share or the methods they can employ. The discussion is focused solely on the reduction of order aspect, with future steps like variation of parameters acknowledged but not yet addressed.

s3a
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Homework Statement


Find the general solution for the equation

(x - 1)y'' - xy' + y = sin(x), x > 1

Given that y_1(x) = e^x satisfies the associated homogeneous equation.


Homework Equations


y_2 = v_2(x) * y_1


The Attempt at a Solution


I read http://tutorial.math.lamar.edu/Classes/DE/ReductionofOrder.aspx and attempted to replicate its method several times and I am attaching my latest attempt. The website I linked to says "Note that upon simplifying the only terms remaining are those involving the derivatives of v. The term involving v drops out. If you’ve done all of your work correctly this should always happen." but I have a term involving v that did not drop out. Also, am I supposed to ignore sin(x) or not? Based on the way the question is phrased, I'd now say I should of ignored it (please tell me if I am correct in saying this) but it doesn't matter for what I am questioning.

By the way, this thread is just about the reduction of order part. (The next step is variation of parameters but I haven't gotten there yet.)

Any help would be greatly appreciated!
Thanks in advance!
 

Attachments

  • MyWork.jpg
    MyWork.jpg
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s3a said:

Homework Statement


Find the general solution for the equation

(x - 1)y'' - xy' + y = sin(x), x > 1

Given that y_1(x) = e^x satisfies the associated homogeneous equation.

Homework Equations


y_2 = v_2(x) * y_1

The Attempt at a Solution


I read http://tutorial.math.lamar.edu/Classes/DE/ReductionofOrder.aspx and attempted to replicate its method several times and I am attaching my latest attempt. The website I linked to says "Note that upon simplifying the only terms remaining are those involving the derivatives of v. The term involving v drops out. If you’ve done all of your work correctly this should always happen." but I have a term involving v that did not drop out. Also, am I supposed to ignore sin(x) or not? Based on the way the question is phrased, I'd now say I should of ignored it (please tell me if I am correct in saying this) but it doesn't matter for what I am questioning.

By the way, this thread is just about the reduction of order part. (The next step is variation of parameters but I haven't gotten there yet.)

Any help would be greatly appreciated!
Thanks in advance!
Check your algebra.

There is no term left involving v.
 
I found that the ve^x is supposed to be vxe^x such that they do cancel out (thanks) but now I'm stuck again. Could you please tell me what I am doing wrong now?

If I'm right so far, I don't see how what I did yields y = x.
 

Attachments

  • MyWork.jpg
    MyWork.jpg
    71 KB · Views: 422
You got v' correctly,

[tex]v'=C_1e^{-x}(x-1)[/tex].

Integrate, add second constant, multiply by ex.

ehild
 
Sorry for the late reply but thanks :).
 
Better late than never:wink:

ehild
 
Lol ya. :D
 

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