Inverse Laplace Transform

  • Thread starter kiwifruit
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  • #1
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Homework Statement


the questions asks to determine inverse laplace transform of

s/(s+4)^4



Homework Equations





The Attempt at a Solution


this can supposedly be done just using laplace transform tables so im guessing i need to simplify that to something thats workable but i dont know how.
the solution is
e^(-4t) (t^2/2 - (2/3) t^3)
anyone can help in directing me how to simplify that equation before i use tables to inverse?
 

Answers and Replies

  • #2
I like Serena
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Welcome to PF, kiwifruit! :smile:

Which transforms can you find that are somewhat close to your question?
Or transforms that perhaps may be of help?
 
  • #3
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i would say
laplace of e^at = 1/(s-a)
or
laplace of cos(at) = s/(s^2 + a^2)
is similar to the question but i dont see how to simplify or factorize it to something workable
 
  • #5
LCKurtz
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I find this formula frequently helpful:

[tex]\mathcal L^{-1}f(s+a) = e^{-at}\mathcal L^{-1}f(s)[/tex]

If you rewrite the expression like this:
[tex]\frac{(s+4)-4}{(s+4)^3}[/tex]
and break it apart, the answer should fall right out.
 

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