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: Derivative Problem

  1. Apr 26, 2009 #1
    1. The problem statement, all variables and given/known data
    I have to find the min and max of this function using derivatives:

    (e^(-x)) - (e^(-2x))

    3. The attempt at a solution
    f'(x) = -e^(-x) + 2x(e^(-2x))
    So now i set that to zero, and I get...

    2x(e^(-2x)) = e^(-x)

    And at this point I have no idea what to do. If you divide e^-x by e^-2x can u do something with the exponents?
  2. jcsd
  3. Apr 26, 2009 #2
    Double check your derivative, you shouldn't be bringing an x down right? The derivative of ecx for a constant c is just cecx
  4. Apr 26, 2009 #3
    o i ggot it! so it become

    2 = e^(-x-2x)
    and then you simply take the ln...

    thanks jeffreydk
  5. Apr 26, 2009 #4
    No problem.

    Watch out though, I think you have a sign error in there.


    So then 2e-2x=e-x

    and therefore by dividing you get 2=e-x+2x
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook