1. Limited time only! Sign up for a free 30min personal 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 differentiation dy/dx=xy^2

  1. May 6, 2008 #1
    1. The problem statement, all variables and given/known data
    If dy/dx=xy^2 and x=1 when y=1, then y=

    (A) x^2
    (B) -2/(x^2 -3)
    (C) x^2 + 3
    (D) 2/(x^2 +1)
    (E) (x^2 -3)/2

    2. Relevant equations

    3. The attempt at a solution

    dy/y^2=x dx
    ∫dy/y^2=∫x dx
    -1/y = x^2/2 + C
    y=-2/x^2 + C
    1=-2/1^2 + C
    y=-2/x^2 +3

    but thats not the answer...

    please help i have the AP test tomorrow.
    much appreciated
  2. jcsd
  3. May 6, 2008 #2


    User Avatar

    Watch the step between line 5 and 6. f(x) = x^-1 is not linear.
  4. May 6, 2008 #3
    That's not really implicit differentiation -- it's a diff. eq.
  5. May 6, 2008 #4

    when i integrate, it's y^-1/-1 right? not just y^-1
  6. May 6, 2008 #5
    Nevermind I got it.
    Answer is B :)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook