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Math Help - Second and third order differential equations

  1. #1
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    Smile Second and third order differential equations

    I need your help to solve the following differential equations:

    1) y''' - y' = e^x

    and

    2) y'' - xy' = sinx

    Thank you,
    Last edited by mr fantastic; April 15th 2010 at 03:51 PM. Reason: Changed post title
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  2. #2
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    Quote Originally Posted by essedra View Post
    I need your help to solve the following differential equations:

    1) y''' - y' = e^x

    and

    2) y'' - xy' = sinx

    Thank you,
    In both cases substitute v = y'. The first DE becomes second order with constant coefficients. The second DE then gets done using the integrating factor method. Both are in your class notes and textbook.

    Then solve for v. And hence solve for y.

    If you need more help, please show all that you've done and say where you get stuck.
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  3. #3
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    Question

    I guess the method is same with the 2nd order diff. equations, so for the non-homogeneous part, I should use Undetermined Coefficients or Variation of Parameters?
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  4. #4
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    Quote Originally Posted by essedra View Post
    I guess the method is same with the 2nd order diff. equations, so for the non-homogeneous part, I should use Undetermined Coefficients or Variation of Parameters?
    Yes.
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