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Help me to explain this

  1. Nov 5, 2009 #1
    1. The problem statement, all variables and given/known data

    I have my notes below, however I don't understand the part where it says that:

    xp(t) = A, where did this come from?

    http://img142.imageshack.us/img142/4733/questionub.th.jpg [Broken]

    2. Relevant equations



    3. The attempt at a solution
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Nov 5, 2009 #2

    tiny-tim

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    Homework Helper

    Hi -EquinoX-! :smile:

    You have x'' -6x' + 5x = 5.

    The general solution is the characteristic solution plus any particular solution.

    For the particular solution, you make an intelligent guess …

    in this case, it seems obvious that a constant will do (in fact, I don't know why he bothered to say let xp(t) = A, and solve for A … I'd just have gone straight to xp(t) = 1)

    (but if there was a 5x on the RHS, you'd choose a linear function, if there was an e7x, a multiple of e7x, and so on)
     
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