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Homework Help: Laplace Transform question with unit step function

  1. May 7, 2015 #1
    1. The problem statement, all variables and given/known data


    2. Relevant equations
    Laplace Trasformations

    3. The attempt at a solution
    a. done
    b. f(t)= t -3*t*u(t-1) + 4*u(t-1) -3*u(t-2) -2*t*(t-2)
    c. 1/(s^2) - (3e^-s -2e^-2s)/(s^3) + (4e^-s -3e^-2s)/s
    d. 1/(s-1) * (1/(s^2) - (3e^-s -2e^-2s)/(s^3) + (4e^-s -3e^-2s)/s)

    These are the answers i got but my friend got all different ones and we are not sure who is correct. Thanks for any help.
  2. jcsd
  3. May 7, 2015 #2

    Ray Vickson

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    Science Advisor
    Homework Helper

    The first 4 terms on the right of (b) are OK but the fifth term is incorrect. You should develop the habit of always checking these things for yourself; just look at f(t) and your right-hand-side for 0 < t < 1, then for 1 < t < 2, then for t > 2. What does your answer in (b) look like for t > 2?
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