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Math Help - find the inverse of the laplace transform

  1. #1
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    find the inverse of the laplace transform

    ok well here is the problem..





    and here is my answer,

    im not seeing where i went wrong, used partial fractions to break it down, i figured out A to be 1/3 and B to be 2/3...

    any help would be appreciated, thanks in advance
    Last edited by mr fantastic; April 21st 2011 at 11:51 PM.
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  2. #2
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    Your partial fractions are wrong.

    It should be A/s + B/(s + 3) = 1/(s^2 + 3s)

    [A(s + 3) + Bs]/[s(s + 3)] = 1/[s(s + 3)]

    A(s + 3) + Bs = 1

    As + 3A + Bs = 1

    (A + B)s + 3A = 0s + 1

    A + B = 0 and 3A = 1

    A = 1/3 and B = -1/3.


    So 1/(s^2 + 3s) = 1/(3s) - 1/[3(s + 3)]. Now find the inverse Laplace transform.
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  3. #3
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    nevermind i caught it, it was soooo simple. 0 = As + Bs LOL yup im a lil tired...
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