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Inverse laplace transform

  1. Dec 10, 2011 #1
    1. The problem statement, all variables and given/known data

    I'm attempting to find the inverse laplace transform of (5/((2x+3)(4+x^2)))




    3. The attempt at a solution

    Here's the solution:
    http://www.wolframalpha.com/input/?i=inverse+laplace+transform+(5/((2x+3)(4+x^2)))

    There's 3 terms in the solution and 2 are trigonometric. But according to laplace tables you
    only get a trigonometric term if a variable in one of the terms of the denominator is squared and if you perform PFE there won't be any variables squared so I'm not sure what's going on here.
     
  2. jcsd
  3. Dec 10, 2011 #2
  4. Dec 10, 2011 #3

    vela

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    Did you actually do the partial fractions expansion?
     
  5. Dec 10, 2011 #4
    How do you work out that term for the PFE?



    Using this method I got the correct answer for the 2nd term but not the term with x^2 as the denominator.

    4+x^2 = 0
    so the limit is at x = 2

    sub x = 2 into
    5/(2x+3) to get the value of the residual then
    the final answer is 5/7(4+x^2)
     
  6. Dec 10, 2011 #5
    Worked it out, I needed Bx + C as the residual and not just B.
     
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