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!

Solving w e^x

  1. May 26, 2005 #1
    how do i solve
    [tex]e^x+e^{3x}-1=0[/tex]
    for x?
     
  2. jcsd
  3. May 26, 2005 #2
    to make it simple let y=e^x

    thus giving y^3 + y - 1 = 0
    y(y^2 + 1) = 1

    i looked at this quickly and i don't think that you would get a solution for x.
     
    Last edited: May 26, 2005
  4. May 26, 2005 #3

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Let y= ex and the equation becomes y3+ y- 1= 0. Can you solve that?
     
  5. May 26, 2005 #4
    how can the answer be x=0?
    [tex]e^{x}+e^{3x}-1=0[/tex]
    [tex]e^{0}+e^{3\times{0}}-1=0[/tex]
    [tex]1+1-1=0[/tex]
    [tex]1=0[/tex]??
     
  6. May 26, 2005 #5
    the answer cannot be zero, i edited my post (sorry about that)
     
  7. May 26, 2005 #6
    no prob, but is there really no solution?
     
  8. May 26, 2005 #7
    well it makes sense to me because this is a cubic function right? how did you go about solving for y?
     
  9. May 26, 2005 #8
    i didn't, i don't know how to
     
  10. May 26, 2005 #9

    Zurtex

    User Avatar
    Science Advisor
    Homework Helper

    There is 1 real answer and 2 initial complex answers, being non-simple roots of the cubic equation they all look quite nasty.
     
  11. May 26, 2005 #10
    could someone explain how to find the real answer?
     
  12. May 26, 2005 #11

    dextercioby

    User Avatar
    Science Advisor
    Homework Helper

    Check out Mathworld's page on the cubic equation.

    Daniel.
     
  13. May 26, 2005 #12
    ok, thanks
     
  14. May 27, 2005 #13
    you can set
    [tex] y=e^x[/tex]
    then the equation will become [tex] y+y^3-1=0 [/tex]
    now you can creat the term [tex] y^2 [/tex],then minus the same term.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Solving w e^x
  1. Solve |x-1|e^x (Replies: 2)

  2. Solving for X (Replies: 5)

Loading...