Results 1 to 5 of 5

Thread: Partial fractions

  1. #1
    Member
    Joined
    Sep 2008
    Posts
    239

    Partial fractions

    1. a) Express (x+3)/x(x-1) in terms of partial fractions

    b) Find ∫(x+3)/x(x-1)dx

    Not sure if i need to expand the denominator in a?

    really have no idea how to do b!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Sep 2008
    From
    West Malaysia
    Posts
    1,261
    Thanks
    1
    Quote Originally Posted by djmccabie View Post
    1. a) Express (x+3)/x(x-1) in terms of partial fractions

    b) Find ∫(x+3)/x(x-1)dx

    Not sure if i need to expand the denominator in a?

    really have no idea how to do b!
    $\displaystyle \frac{x+3}{x^2(x-1)} $

    $\displaystyle = \frac{A}{x} + \frac{B}{x^2} + \frac{C}{x-1}$
    Last edited by mathaddict; Mar 2nd 2009 at 07:28 AM. Reason: mistake .
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    16,216
    Thanks
    3702
    Quote Originally Posted by djmccabie View Post
    1. a) Express (x+3)/x(x-1) in terms of partial fractions

    b) Find ∫(x+3)/x(x-1)dx

    Not sure if i need to expand the denominator in a?

    really have no idea how to do b! that's why you do (a) first
    $\displaystyle
    \frac{x+3}{x^2(x-1)} = \frac{A}{x} + \frac{B}{x^2} + \frac{C}{x-1}
    $

    $\displaystyle x+3 = Ax(x-1) + B(x-1) + Cx^2$

    let $\displaystyle x = 1$ ... $\displaystyle C = 4$

    let $\displaystyle x = 0$ ... $\displaystyle B = -3$

    let $\displaystyle x = 2$ ... $\displaystyle A = -4$


    $\displaystyle \int \frac{x+3}{x^2(x-1)} \, dx = \int -\frac{4}{x} - \frac{3}{x^2} + \frac{4}{x-1} \, dx
    $
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Sep 2008
    Posts
    239
    hi just a question. When you let x=2, what happens to B and C ?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor

    Joined
    Apr 2005
    Posts
    19,795
    Thanks
    3035
    Replace them with the values you already had: B= -3, C= 4.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 0
    Last Post: Apr 28th 2010, 09:53 AM
  2. Partial Fractions
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: Feb 4th 2010, 06:24 PM
  3. Partial Fractions
    Posted in the Pre-Calculus Forum
    Replies: 9
    Last Post: Jan 17th 2010, 02:20 AM
  4. Help on Partial Fractions
    Posted in the Calculus Forum
    Replies: 12
    Last Post: Jan 6th 2010, 03:00 AM
  5. partial fractions
    Posted in the Algebra Forum
    Replies: 1
    Last Post: Jan 21st 2007, 04:49 AM

Search Tags


/mathhelpforum @mathhelpforum