Results 1 to 2 of 2

Math Help - help with implicit differentiation

  1. #1
    Junior Member LexiRae's Avatar
    Joined
    Apr 2008
    Posts
    25

    help with implicit differentiation

    on the curve x + xy + 2y^2 = 6 what is the slope of the line tangent to the curve at the point (2,1)

    i found the derivative:
    1 + x(dy/dx) +y(1) +4y(dy/dx) =0
    i solved and got dy/dx = -1(y+1)/4xy
    but when i put the point 2,1 in i didnt get an answer they gave you. (i got -1/4, its a multiple choice problem and its not there). what am i doing wrong?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Nov 2008
    From
    France
    Posts
    1,458
    When you solve you get dy/dx = -(y+1)/(x+4y)
    which makes -1/3 for (2,1)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 2
    Last Post: July 26th 2010, 05:24 PM
  2. implicit differentiation
    Posted in the Calculus Forum
    Replies: 3
    Last Post: May 1st 2010, 07:42 AM
  3. Implicit Differentiation
    Posted in the Calculus Forum
    Replies: 4
    Last Post: April 28th 2010, 03:19 PM
  4. Implicit differentiation
    Posted in the Calculus Forum
    Replies: 3
    Last Post: April 26th 2010, 05:41 PM
  5. Implicit Differentiation
    Posted in the Calculus Forum
    Replies: 3
    Last Post: March 25th 2008, 07:33 PM

Search Tags


/mathhelpforum @mathhelpforum