Results 1 to 6 of 6

Math Help - Ln problem

  1. #1
    Newbie
    Joined
    Mar 2008
    Posts
    16

    Ln problem

    Hi

    Im halfway though a homework problem and i was hoping for a little insight into how one would go about solving the problem.

    Thanks for whatever you can offer!

    The question:

    \ln(y+\sqrt{2y-1})+\ln(y-\sqrt{2y-1})=0

    So far ive got them all to the same side, added the logs and brought it down to \ln(y^2-2y-1)=0 and was wondering how to remove the ln in order to solve the equation?

    Thank you very much
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Math Engineering Student
    Krizalid's Avatar
    Joined
    Mar 2007
    From
    Santiago, Chile
    Posts
    3,654
    Thanks
    13
    It's actually \ln(y^2-2y+1)=0, and this is pretty familiar.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Mar 2008
    Posts
    16
    So why not give us a clue?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Senior Member Peritus's Avatar
    Joined
    Nov 2007
    Posts
    397
    here's a big clue:

    if:

    \ln \left( {y^2  - 2y + 1} \right) = 0<br />

    then:

    y^2  - 2y + 1 = 1<br />

    can you continue?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Mar 2008
    Posts
    16
    Yeah, i think so; thanks.

    I just had to raise each side as a power of e to get rid of ln right?
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Super Member
    Joined
    Oct 2007
    From
    London / Cambridge
    Posts
    591
    Quote Originally Posted by farso View Post
    Yeah, i think so; thanks.

    I just had to raise each side as a power of e to get rid of ln right?
    yeah, that step is commonly refereed to as "anti-logging"
    Follow Math Help Forum on Facebook and Google+

Search Tags


/mathhelpforum @mathhelpforum