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Homework Help: Finding partial fraction expansions

  1. Feb 4, 2009 #1
    1. The problem statement, all variables and given/known data

    3. Find the partial fraction expansions of the following polynomials

    a) 10/[(s^2)(s^2+6s+10)]

    3. The attempt at a solution
    I assume i should expan the polynomial in the form A/s^2+B/s+(Cs+D)/(s^2+6s+10) but i stuck at finding B. Maybe my expansion is just wrong .. :(
  2. jcsd
  3. Feb 4, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    The form of the expansion is correct. It should work.
  4. Feb 4, 2009 #3


    Staff: Mentor

    The main idea is that the equation
    [tex]\frac{A}{s^2} + \frac{B}{s} + \frac{Cs + D}{s^2 + 6s + 10} = \frac{10}{s^2(s^2 + 6s + 10)} [/tex]
    has to be true for any value of s except those that make one or more denominators vanish. If you pick four values of s you should get four equations in four unknowns, from which you should be able to get A, B, C, and D.
  5. Feb 4, 2009 #4
    Have found C?

    C and B are related ...
  6. Mar 12, 2009 #5
    got it. thanks all
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