1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: Verifying a solution to DE. totally stuck

  1. Apr 26, 2010 #1
    1. The problem statement, all variables and given/known data

    verify that y_1(t) = t is solution of t^2y'' - t (t+2)y' + (t+2)y = 0

    use "reduction of order to find 2nd linerary independent solution of equation

    2. Relevant equations

    I am stuck on the first part. Confused as to how (which method) im expected to use to verify.
    im stuck on getting the characteristic because of all the extra t's in the eqn.
    im used to something with just y's like this: y'' + 5y' -7y = 0
    but i dont know how to treat the t's

    also when i try getting integrating factor, it doesnt work because its 2nd order (right?)
    please help im totally stuck thanks
    3. The attempt at a solution
  2. jcsd
  3. Apr 26, 2010 #2


    User Avatar
    Homework Helper
    Gold Member

    Simple. Substitute [itex]y=t[/itex] into your differential equation...if you get 0=0 as a result, then it satisfies the DE.

    This isn't a constant coefficients problem, you aren't looking for the characteristic polynomial. You are supposed to use reduction of order instead.

    Basically, once you verify that [itex]y_1(t)=t[/itex] is a solution, you look for a second, linearly independent solution, of the form [itex]y_2(t)=u(t)y_1(t)=tu(t)[/itex] by substituting this assumed form into your DE and solving the resulting DE you get for [itex]u(t)[/itex].

    I'm sure your textbook covers this method, so if you have difficulties, try opening your textbook and reading the relevant section :wink:
  4. Apr 26, 2010 #3
    Thanks I figured this out. btw the textbook for this class is $197! its crazy. Professor always seem to make it so complicated too, so i just learn it all on youtube.
    thanks for the help
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook