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!

I need help with integration using partial fractions

  1. Sep 25, 2009 #1
    1. The problem statement, all variables and given/known data

    Compute the integral:
    int ((1-x^2)/(x^3+x)) dx



    2. Relevant equations
    int ((1-x^2)/(x^3+x)) dx


    3. The attempt at a solution
    I think I should use the partial fraction method to simplify the fraction
    so
    (1-x^2)/(x^3+x)= A/x + B/ (1+x^2)
    Therefore
    A(1+x^2)+B(x)=1-x^2
    putting it in a polynomial form:
    x^2 (A)+x (B) + 1 (A)= 1- x^2
    and by equating the coefficients,
    A = -1
    B = 0
    However, A doesn't satisfy the constant on the LHS (+1)

    So what is the thing that I did wrong??

    Thanks in advance
     
  2. jcsd
  3. Sep 25, 2009 #2

    lanedance

    User Avatar
    Homework Helper

    I think you missed the quadratic part of your partial fraction decomposition, it should be

    [tex] \frac{1-x^2}{x(1+x^2)}= \frac{A}{x}+\frac{B+Cx}{1+x^2} [/tex]
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: I need help with integration using partial fractions
Loading...