1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Implicit Differntation

  1. Apr 11, 2009 #1
    I've been working on this problem for a while and can't see my mistake, in the book the answer is stated as being 3, but I end up getting 13.5.

    1. The problem statement, all variables and given/known data
    If x^2+3y^2+2y = 10; dx/dt = 2, x=3 and y = -1 find dy/dt

    3. The attempt at a solution
    d/dt[x^2+3y^2+2y] = d/dt[10]

    3x^2 (dx/dt) + 6y(dy/dt) + 2 (dy/dt) = 0

    6y (dy/dt) + 2 (dy/dt) = -3x^2 (dx/dt)

    dy/dt (6y+2) = -3x^2 (dx/dt)

    dy/dt = -3x^2 (dx/dt) / 6x+2

    dy /dt = -3(3^2)(2) / 6(3)+2 = 13.5
     
  2. jcsd
  3. Apr 11, 2009 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi Iron_Brute! :smile:

    (try using the X2 tag just above the Reply box :wink:)
    erm :redface:

    either it's x3 in the question or it's 2x in the derivative :wink:
     
  4. Apr 11, 2009 #3
    Ugh I can't believe it, it's x^2 in the text but I wrote x^3 on my sheet. Thanks for the help (and the tip on writing the exponents didn't know that), I can't believe I spent so much time looking my problem over and didn't see that. :blushing:
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Implicit Differntation
  1. Implicit applications (Replies: 16)

Loading...