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 logarithm problem for Y

  1. Aug 23, 2008 #1
    (For those values of x for which a solution exists), solve the following equation for y

    3e3y-6 = 2x2-1

    What does it mean by the values of x exists??
    Last edited: Aug 23, 2008
  2. jcsd
  3. Aug 23, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: logarithm

    Because of the nature of the domain of the logarithm one can not evaluate [itex]y=\ln x[/itex] for all x. Specifically the domain of the logarithm is all positive numbers. Therefore, we say that no solution exists for [itex]y=\ln x[/itex] in the domain [itex]x\in\left(-\infty, 0\right][/itex].

    So the question is asking you to solve the equation for y, for all values of x which exist. I hope that makes sense.
    Last edited by a moderator: Aug 23, 2008
  4. Aug 23, 2008 #3
    Re: logarithm

    Say you have [tex]ln(x)=y[/tex].
    This could be seen as [tex]e^y=x[/tex]
    It is impossible to raise any real number to any power and have it equal 0 or any number below that (feel free to try, in fact, I encourage it). Since it can't exist as [tex]x\in(-\infty,0)[/tex], there are only certain numbers it can exist as.
  5. Aug 23, 2008 #4


    User Avatar
    Science Advisor
    Homework Helper

    Hi fr33pl4gu3! :smile:

    Simple answer:

    3e3y-6 can only be positive.

    So the equation doesn't work if 2x2-1 is negative or zero. :smile:
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Solving logarithm problem for Y
  1. Solving logarithms (Replies: 3)

  2. Solving for y (Replies: 3)

  3. Solving for y (Replies: 6)

  4. Solve logarithm (Replies: 14)