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Homework Help: 2nd Order Linear ODE (tough)

  1. May 13, 2015 #1


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    Gold Member

    1. The problem statement, all variables and given/known data
    $$ay''-(2x+1)y'+2y=0$$ subject to ##y(0)=1## and ##y(1)=0## where ##a## is a non-zero constant.

    2. Relevant equations
    Not too sure

    3. The attempt at a solution
    I know an analytic solution exists since I solved with mathematica. My thoughts were to try a series expansion, but since the analytic solution is in closed form and is using the imaginary error function, I'd rather not waste a lot of time with a power series guess if someone knows (or sees) something insightful.

    Any ideas or clever tricks?

  2. jcsd
  3. May 13, 2015 #2


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    Science Advisor

    I would use two methods. First, let u= 2x+ 1. Then du/dx= 2 so [itex]dy/dx= (dy/du)(du/dx)= 2(dy/du)[/itex] and [itex]d^2y/dx^2= (d/dx)(dy/dx)= d/dx(2dy/du)= 4 d^2y/du^2[/itex]. So the equation becomes [itex]4\alpha d^2y/du^2- 2udy/d+ 2y= 0[/itex].

    Now look for a power series solution. Let [itex]y= \sum_{n=0}^\infty a_nu^n[/itex].
    Content abridged by a mentor.
    Last edited by a moderator: May 13, 2015
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