Results 1 to 4 of 4

Math Help - evaluating a definite integral

  1. #1
    Member
    Joined
    May 2012
    From
    Toronto
    Posts
    244
    Thanks
    1

    evaluating a definite integral

    if I evaluate

    evaluating a definite integral-picture-19.png

    I get e^6 - e^2 but the answer should be (1/2)(e^6 - e^2), where does the (1/2) come from?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Sep 2012
    From
    Australia
    Posts
    3,660
    Thanks
    606

    Re: evaluating a definite integral

    Hey kingsolomonsgrave.

    Try doing a transformation u = 2x where du/dx = 2 which means you have to multiply by a 1/2 and the limits go from [1,3] to [2,6]
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor MarkFL's Avatar
    Joined
    Dec 2011
    From
    St. Augustine, FL.
    Posts
    1,988
    Thanks
    734

    Re: evaluating a definite integral

    The reason your answer is wrong is because:

    \frac{d}{dx}\left(e^{2x} \right)\ne e^{2x}

    but:

    \frac{d}{dx}\left(\frac{1}{2}e^{2x} \right)=e^{2x}

    Using the substitution suggested by chiro is the best way to go, IMHO.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    May 2012
    From
    Toronto
    Posts
    244
    Thanks
    1

    Re: evaluating a definite integral

    thanks!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Evaluating a definite integral
    Posted in the Calculus Forum
    Replies: 2
    Last Post: June 8th 2012, 07:19 AM
  2. Evaluating the definite integral
    Posted in the Calculus Forum
    Replies: 2
    Last Post: December 18th 2009, 10:05 AM
  3. Replies: 4
    Last Post: May 29th 2009, 03:21 AM
  4. Evaluating this definite integral
    Posted in the Calculus Forum
    Replies: 3
    Last Post: February 17th 2009, 05:33 PM
  5. Evaluating a definite integral
    Posted in the Calculus Forum
    Replies: 4
    Last Post: January 26th 2009, 06:20 PM

Search Tags


/mathhelpforum @mathhelpforum