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Homework Help: Easy differential equation question

  1. Nov 2, 2008 #1

    rock.freak667

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    1. The problem statement, all variables and given/known data

    Obtain the ordinary differential equations whose solution is
    i)y=Ae2x+Bxe2x
    ii)y=mx+ h/m where h is a constant and m is to be eliminated

    2. Relevant equations



    3. The attempt at a solution

    For the first one it is simply:
    y''-4y'+4y=0

    For the second one it is just y''=0?
     
    Last edited: Nov 3, 2008
  2. jcsd
  3. Nov 3, 2008 #2

    gabbagabbahey

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    Not quite, y''=0 has a general solution y=Ax+B with no restrictions on A or B....you want an ODE that gives a more restrictive solution, one where A=m and B=(a constant)/m...so you need a more restrictive ODE...try a first order ODE instead of a second order one.
     
  4. Nov 3, 2008 #3

    rock.freak667

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    But if I use a 1st order ODE, I won't eliminate the constant m
     
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