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!

Critical points and 2nd partials test

  1. Apr 3, 2009 #1
    1. The problem statement, all variables and given/known data

    Find all critical points of f(x,y) = 12xy-x^2 y-2xy^2 and test them for relative extrema using the 2nd partials test.

    2. Relevant equations

    3. The attempt at a solution

    {0=fx(x,y)=12-2x-2 10x-2 x=5
    {0=fy(x,y)=12-4y y=3

    Critical point: (5,3)

    fxx(x,y)= -2
    fyy(x,y)= -4
    fxy(x,y)= 0

    d=0 no conclusion

    Just wondering if I did this right?
  2. jcsd
  3. Apr 3, 2009 #2


    User Avatar
    Science Advisor

    fxx(5,3)fyy(5,3)= (-2)(-4), not (0)(0)!
  4. Apr 3, 2009 #3
    Ok, so


    Is that right?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Critical points and 2nd partials test
  1. Critical Points (Replies: 3)

  2. Critical points (Replies: 4)