Results 1 to 3 of 3

Math Help - extremely hard partial derivative question

  1. #1
    Newbie
    Joined
    Feb 2010
    Posts
    20

    solved

    thanks for the helppp
    Last edited by goaway716; October 31st 2010 at 01:46 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Behold, the power of SARDINES!
    TheEmptySet's Avatar
    Joined
    Feb 2008
    From
    Yuma, AZ, USA
    Posts
    3,764
    Thanks
    78
    Quote Originally Posted by goaway716 View Post
    If f_x and f_y are the partial derivatives of f(x,y) and f_s and f_t are the partial derivatives of f viewed as a function of s and t, show that if:

    s=(x^3)-(3xy)

    t=3xy-y^3

    then

    xf_x+yf_y=3(sf_s+tf_t)

    please help me finishing this problem as i got no clue how to go about it
    thanx
    You need to use the chain rule.

     \displaystyle \frac{\partial f}{\partial x}=\frac{\partial f}{\partial s}\frac{\partial s}{\partial x} + \frac{\partial f}{\partial t}\frac{\partial t}{\partial x}

     \displaystyle \frac{\partial f}{\partial y}=\frac{\partial f}{\partial s}\frac{\partial s}{\partial y} + \frac{\partial f}{\partial t}\frac{\partial t}{\partial y}

    Then just calculate

    \displaystyle xf_x+yf_y= and simplify and sub out x's and y's for s's and t's.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Apr 2013
    From
    malaysia
    Posts
    1

    Re: extremely hard partial derivative question

    i have a question and i make a half of it but it is really hard, i had try so many times but did not get the answer.., please help me to find the answer., sorry for my bad english..IMG.pdf.., only number 1 but ignore du/dx+dv/dy=0.., because i already prove it...
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Extremely Hard Max/Min Problem
    Posted in the Calculus Forum
    Replies: 5
    Last Post: April 7th 2011, 12:43 PM
  2. Extremely hard calculus question.
    Posted in the Calculus Forum
    Replies: 3
    Last Post: June 23rd 2010, 11:51 AM
  3. A hard inverse tan partial derivative
    Posted in the Calculus Forum
    Replies: 1
    Last Post: March 20th 2009, 04:12 AM
  4. Extremely hard minimization problem
    Posted in the Calculus Forum
    Replies: 5
    Last Post: October 7th 2008, 02:33 AM
  5. Hard question - nth derivative
    Posted in the Calculus Forum
    Replies: 3
    Last Post: November 24th 2007, 07:59 AM

Search Tags


/mathhelpforum @mathhelpforum