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Easy differential equation but i am stuck

  1. Feb 20, 2012 #1
    1. The problem statement, all variables and given/known data
    What is the general solution of tv' + v = 0?
    book says it is v(t) = c/t but i dont see how
    i tried to solve like this:

    v' + (1/t)v = 0

    p(t) = 1/t
    P(t) = Ln(t)

    y = e^ln(t) + c

    = t + e^c

    please help,thanks



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Feb 20, 2012 #2

    lanedance

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    what is y?

    your first equation is separable, write v'=dv/dt, then move all terms with a v to the LHS and all terms with a t to the RHS then integrate both sides
     
  4. Feb 20, 2012 #3

    vela

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    This isn't right. What you're doing by calculating ##e^{\int p(t)\,dt}## is finding an integrating factor, not the solution to the differential equation. Check your textbook to see what you're supposed to do with this factor.

    (Or solve the problem the way lanedance suggested.)
     
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