Results 1 to 4 of 4

Math Help - Proof of logarithms

  1. #1
    Member
    Joined
    Sep 2009
    Posts
    145

    Proof of logarithms

    Hello,

    I'm at a lost as to what to do here. I asked a teacher for help and he said these are based on certain kinds of logarithmic proof, but I've not been taught then.
    If these really are based on certain logarithmic proofs, can someone fill me in on it so I can try the questions, please.

    Prove the following:
    1) 1/logxXYZ + 1/logyXYZ + 1/logzXYZ = 1 =>NUMERATOR IS 1.

    2) if a, b and c are positive real integers, then (log ab)(log bc)= (log ac)
    Last edited by Hellbent; September 28th 2009 at 01:24 PM. Reason: Error in question
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by Hellbent View Post
    Hello,

    I'm at a lost as to what to do here. I asked a teacher for help and he said these are based on certain kinds of logarithmic proof, but I've not been taught then.
    If these really are based on certain logarithmic proofs, can someone fill me in on it so I can try the questions, please.

    Prove the following:
    1) log xxyz + log yxyz + log zxyz = 1
    If this means:

    \log_x(x.y.z)+\log_y(x.y.z)+\log_z(x.y.z)=1

    its not true, which can be seen by putting z=y=z=a, then the left hand side is:

    3\log_a(a^3)=9

    CB
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by Hellbent View Post
    2) if a, b and c are positive real integers, then (log ab)(log bc)= (log ac)
    To do this you need to know that:

    \log_x(y)=\frac{\log(y)}{\log(x)}

    where a \log without subscript means a logarithm to any base.

    CB
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Sep 2009
    Posts
    145

    Answer

    2.) (logaB)(logbC)= (logaB)(logaC)/(logaB)
    = logaC
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Help with logarithms
    Posted in the Algebra Forum
    Replies: 7
    Last Post: May 8th 2011, 10:38 PM
  2. Proof of Logarithms
    Posted in the Algebra Forum
    Replies: 5
    Last Post: April 10th 2011, 06:28 PM
  3. Easy proof - Logarithms
    Posted in the Calculus Forum
    Replies: 1
    Last Post: December 14th 2009, 06:09 AM
  4. logarithms
    Posted in the Algebra Forum
    Replies: 1
    Last Post: January 14th 2008, 04:05 PM
  5. Logarithms
    Posted in the Algebra Forum
    Replies: 13
    Last Post: January 11th 2008, 11:17 AM

Search Tags


/mathhelpforum @mathhelpforum