Results 1 to 4 of 4

Math Help - integration, rough stuff

  1. #1
    Junior Member winterwyrm's Avatar
    Joined
    Oct 2007
    Posts
    67

    integration, rough stuff

    integral of (x^2)/root(4-x)dx

    integral of e^(4x)/(e^2x-4)^2

    Thanks in advance. ^_^
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Eater of Worlds
    galactus's Avatar
    Joined
    Jul 2006
    From
    Chaneysville, PA
    Posts
    3,001
    Thanks
    1
    \int\frac{e^{4x}}{(e^{2x}-4)^{2}}dx


    You could let u=e^{2x}, \;\ du=2e^{2x}dx, \;\ \frac{du}{2}=e^{2x}dx

    Make the subs and get:

    \frac{1}{2}\int\frac{u}{(u-4)^{2}}du=\frac{1}{2}\left[\int\frac{1}{u-4}du+\int\frac{4}{(u-4)^{2}}du\right]

    These are relatively easy integrals to work with now.

    You can also rearrange it in other ways by using substitutions.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by winterwyrm View Post
    integral of (x^2)/root(4-x)dx
    should it be sqrt(4 - x^2)?

    integral of e^(4x)/(e^2x-4)^2
    a simple substitution can handle this. try u = e^(2x) - 4

    EDIT: Oh, galactus beat me to this one. he used a slightly harder substitution to work with though, i think
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    9,937
    Thanks
    338
    Awards
    1
    Quote Originally Posted by winterwyrm View Post
    integral of (x^2)/root(4-x)dx
    Let u = 4 - x \implies du = -dx

    \int \frac{x^2}{\sqrt{4 - x}}~dx = \int \frac{(4 - u)^2}{\sqrt{u}}~-du

    = -\int\frac{4 - 4u + u^2}{u^{1/2}}~du

    = -\int 4~u^{-1/2}~du + \int 4u^{1/2}~du - \int u^{3/2}~du

    which you should be able to do easily.

    -Dan
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Rough Inclined Plane...
    Posted in the Math Topics Forum
    Replies: 4
    Last Post: December 8th 2011, 02:27 PM
  2. Calculus HW question on Integration and stuff
    Posted in the Calculus Forum
    Replies: 5
    Last Post: April 3rd 2010, 06:39 PM
  3. stuff
    Posted in the Discrete Math Forum
    Replies: 8
    Last Post: July 18th 2009, 02:36 PM
  4. step-ladder on rough floor
    Posted in the Advanced Applied Math Forum
    Replies: 0
    Last Post: April 24th 2009, 01:48 PM
  5. rough stuff
    Posted in the Calculus Forum
    Replies: 0
    Last Post: October 25th 2007, 10:26 AM

Search Tags


/mathhelpforum @mathhelpforum