Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Inhomogenous ODEs, Particular solutions question

  1. May 13, 2007 #1
    1.The position of a particle x(t) obeys the following differential equation

    d^2x/dt^2 + 4(dx/dt) + 3x = (3t/2) -4

    If at t=0, both x=0 and dt/dx=0, find x(t)

    Attempt at solution
    I've found the homogeneous solution to be y=Aexp(-3x) + Bexp(-x), and know how to find x(t) given boundary conditions, but I'm having trouble finding the particular solution. I know you have to use g(x) where g(x) is the RHS of the equation, but when I try using Yp=r exp(mu x) or a combination of factors of x, I get a load of rubbish. Can anyone please help?
  2. jcsd
  3. May 13, 2007 #2


    User Avatar
    Science Advisor
    Homework Helper

    If you look at the form of the RHS, you might guess that a particular solution would have the form x(t)=a*t+b. Put that into the equation at try to find a and b. You first try at finding a particular solution should always be to try and guess what it could be and then prove yourself right.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook