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!

Homework Help: Maximum and Minimum Value Application question

  1. Feb 27, 2010 #1
    1. The problem statement, all variables and given/known data
    Find the value of k if the function y=x^2+kx+72 has a local minimum at x=4
     
  2. jcsd
  3. Feb 27, 2010 #2
    What have you tried for this problem.
     
  4. Feb 27, 2010 #3
    Differentiate the original function and you get y = 2x + k ,and it has a local minimun at x=4.
    Block 4 in and the output(y) should be 0 because of Fermat's theorem (http://en.wikipedia.org/wiki/Fermat's_theorem_(stationary_points))

    So you'll get k = -8 ,is that correct ?
     
  5. Feb 27, 2010 #4
    yes! thankyou so much :)
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook




Loading...