1. Not finding help here? Sign up for a free 30min 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!

Stuck on equating co-efficents! DiffEQ

  1. Feb 24, 2006 #1
    I'm confused on how to equate coniffecents. What i'm doing is, finding a particular solution for just the polynomial then i'm going to find it just for the exponential and add them together rather then putting it all together and making it a mess, but i'm stuck when i try to add the Co-efficents, can someone explain that process to me? Thanks!

    Here is my work!
  2. jcsd
  3. Feb 24, 2006 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    I kinda see.

    Fact: Two polynomials are equal iff their respective coefficients are the same. (You might want to try proving this (hint set x=0. u get 1 relation, differentiate, set x=0, u get a second equality, differentiate, set x=0, etc))

    This is what you have here. So you want to rewrite the LHS as

    [tex]-At^2 + (2A-B)t + (12A+B-C) = t^2 + t[/tex]

    Now what the theorem/fact stated above is telling you is that


    It's a linear system of equation. Start row-reducin' friend!
  4. Feb 24, 2006 #3
    THanks man worked great!!
  5. Feb 25, 2006 #4


    User Avatar
    Homework Helper

    There is another method: just plug-in three different values of t (like, say t=0,1,2,) into the given equation to generate three equations in A,B, and C.
  6. Feb 25, 2006 #5
    thanks for the tip
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?