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Math Help - particular solution of high order 2d

  1. #1
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    particular solution of high order 2d

    y'''' -6y'''+9y''=x

    i take y_p=ax+b

    i get 0=x

    so i cant find the a ,b for the solution
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  2. #2
    Behold, the power of SARDINES!
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    Quote Originally Posted by transgalactic View Post
    y'''' -6y'''+9y''=x

    i take y_p=ax+b

    i get 0=x

    so i cant find the a ,b for the solution
    Your characteristic equation is

    r^4-6r^3+9r^2=0 \iff r^2(r-3)^2

    so the complimentary solution already contains y=ax+b

    Since there is a factor of r^2 you must multiply your guess by x^2 to get ax^3+bx^2
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  3. #3
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    what are they laws tieing the homogeneus and the practical solutions?

    i we have also (r-3)^2 thing
    why its not changing the particular solution too
    ?

    whats the general theory on think link thing
    ?
    i dont know how to search it on google
    Last edited by transgalactic; December 8th 2010 at 12:26 PM.
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  4. #4
    Behold, the power of SARDINES!
    TheEmptySet's Avatar
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    Try this link, it may help.

    The Method of Undetermined Coefficients

    Also try google Method of undetermined coeffients.
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