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Homework Help: Partial fractions

  1. Mar 15, 2009 #1
    1. The problem statement, all variables and given/known data
    1/((x^2-1)^2)


    2. Relevant equations



    3. The attempt at a solution
    so i get (Ax+B)/(x^2-1) + (Cx+D)/((x^2-1)^2)

    then i multiply both sides by ((x^2-1)^2)
    then i get 1=(Ax+B)(x^2-1)+ (Cx+D)

    then i multiply it out Ax^3+Bx^2 -Ax +Cx +D =1
    then i equate the coeffcients
    A=0 B=0 -A+C=0 -B+D=1 D=1

    but when i plug these back in i dont get what my book gets and i setting this up correctly
     
  2. jcsd
  3. Mar 15, 2009 #2

    lurflurf

    User Avatar
    Homework Helper

    that should be
    1/((x^2-1)^2)=A/(x+1)+B/(x+1)^2+C/(x-1)+D/(x-1)^2
     
  4. Mar 15, 2009 #3
    ok i see
     
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