Results 1 to 2 of 2

Math Help - Tricky stationary points

  1. #1
    Newbie
    Joined
    Aug 2008
    Posts
    11

    Tricky stationary points

    What are the stationary points of

    f(x,y) = e^((-x^3) +3x (-y^2))

    and determine their nature.

    Right, so the partial derivative holding y constant is:

    ((-3x^2) + 3 (-y^2))e^((-x^3) +3x (-y^2))

    and holding x constant:

    ((-x^3) + 3x -2y)e^((-x^3) +3x (-y^2))

    Is that correct?
    If so, I make them equal to zero?
    And then find the second partial derivative to determine the nature of the stationary points?

    How the hell do I do that, im not sure im doing it right..

    And apologies for the untidiness of the functions.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by BogStandard View Post
    What are the stationary points of

    f(x,y) = e^((-x^3) +3x (-y^2))

    and determine their nature.

    Right, so the partial derivative holding y constant is:

    ((-3x^2) + 3 (-y^2))e^((-x^3) +3x (-y^2))

    and holding x constant:

    ((-x^3) + 3x -2y)e^((-x^3) +3x (-y^2))

    Is that correct?
    If so, I make them equal to zero?
    And then find the second partial derivative to determine the nature of the stationary points?

    How the hell do I do that, im not sure im doing it right..

    And apologies for the untidiness of the functions.
    f(x,y) = e^{-x^3 -3x y^2}

     <br />
f_x(x,y)=(-3x^2-3y^2)e^{-x^3 -3x y^2}=-3(x^2+y^2)e^{-x^3 -3x y^2}<br />

     <br />
f_y(x,y)=(-6xy)e^{-x^3 -3x y^2}<br />

    RonL
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 3
    Last Post: August 24th 2011, 12:35 PM
  2. Stationary Points, Local points of Extrema
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 19th 2008, 02:44 PM
  3. Please help - Stationary points
    Posted in the Calculus Forum
    Replies: 12
    Last Post: September 19th 2008, 05:05 PM
  4. Stationary Points
    Posted in the Advanced Math Topics Forum
    Replies: 6
    Last Post: February 19th 2008, 09:37 AM
  5. Replies: 3
    Last Post: May 5th 2006, 10:22 AM

Search Tags


/mathhelpforum @mathhelpforum