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!

Second derivative of e^x minus e^x

  1. Jun 28, 2008 #1
    1. The problem statement, all variables and given/known data
    Show that y(t) = e^t is a solution of y'' - y = 0,

    2. Relevant equations
    integral of e^x dx = e^x +c
    derivative of e^x = e^x

    3. The attempt at a solution
    set m = d(e^t)/dt, which also = e^t then dm = e^t

    then d(m)/dt = e^t if y(t) = e^t is a solution
    integrate both sides m= e^t +c
    substitute e^t = e^t + c which is true for C = 0
    not sure if it is that simple
  2. jcsd
  3. Jun 28, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    It's even more simple than that. Put y=e^t. y'=e^t. y''=e^t. y''-y=e^t-e^t=0. You don't need to say much more than that.
  4. Jun 28, 2008 #3
    Thanks Dick! sometimes it just helps to be able to ask someone else to look at it.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Second derivative of e^x minus e^x