Results 1 to 4 of 4

Math Help - double integral problem

  1. #1
    Newbie
    Joined
    Feb 2010
    Posts
    17

    double integral problem

    Use double integral to find the area bounded by the equation:
    y= x(x-2)(x+1) , y=0

    I have attempted it by doing the following:
    For x fixed, y varies from y= x(x-2)(x+1) to y=0
    x varies from x=2 to x=-1
    But while solving the integral i'm not reaching the required answer.

    Can anyone help me out please?
    I have exams this Friday!
    Thanks bunches
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Feb 2010
    Posts
    133

    Area

    Hello,

    If you draw the graph you'll notice that you have two areas. One extending from x_{1}=-1 to x_{2}=0 and the other area extending from x_{2}=0 to x_{3}=2. So correct the limits.

    Furthermore make sure to consider the sign of the integrals (one area is above y=0 and the other is under y=0 ).
    Last edited by surjective; May 4th 2010 at 11:34 AM.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Feb 2010
    Posts
    17
    I have drawn the curve and i am integrating for
    while x is fixed
    y varies from y=0 to y= -x(x-2)(x+1), x varies from x=2 to x=0
    +
    while x is fixed
    y varies from y= x(x-2)(x+1) to y=0, x varies from x=0 to x=-1

    but still i'm not reaching the answer.
    I'm always getting -2.25 as answer when it should have been 37/12

    help please!
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,792
    Thanks
    1532
    Then show what you have done. What did you get for each part of
    \int_{-1}^0 (x^3- x^2- 2x) dx- \int_0^2(x^3- x^2- 2x)dx?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Double Integral Problem
    Posted in the Calculus Forum
    Replies: 1
    Last Post: November 20th 2011, 05:40 PM
  2. Double integral problem
    Posted in the Calculus Forum
    Replies: 2
    Last Post: December 18th 2010, 11:11 PM
  3. The double integral of this problem.
    Posted in the Calculus Forum
    Replies: 4
    Last Post: March 23rd 2010, 06:23 PM
  4. Double integral problem!
    Posted in the Calculus Forum
    Replies: 1
    Last Post: April 28th 2009, 09:50 PM
  5. Double Integral Problem
    Posted in the Calculus Forum
    Replies: 0
    Last Post: February 11th 2009, 07:14 PM

Search Tags


/mathhelpforum @mathhelpforum