Results 1 to 10 of 10

Math Help - Natural Logarithms Help Plz!

  1. #1
    Junior Member
    Joined
    Feb 2008
    Posts
    74

    Natural Logarithms Help Plz!

    I managed to do all of my homework except this one:

    How do you solve the equation: ln x - ln 5= -1??
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member Peritus's Avatar
    Joined
    Nov 2007
    Posts
    397
    \begin{gathered}<br />
  \ln x - \ln 5 =  - 1 \hfill \\<br />
  \ln \frac{x}<br />
{5} =  - 1 \hfill \\<br />
   \Leftrightarrow \frac{x}<br />
{5} = e^{ - 1}  \hfill \\<br />
   \Leftrightarrow x = 5e^{ - 1}  \hfill \\ <br />
\end{gathered} <br />
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Feb 2008
    Posts
    74
    how did you do that? You divide the numbers x and 5 together?

    And after that I just find out what e^-1 is?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by topaz192 View Post
    how did you do that? You divide the numbers x and 5 together?
    it is a rule

    \log_a x - \log_a y = \log_a \frac xy

    And after that I just find out what e^-1 is?
    no. leave it as e^{-1}. or you can write the answer as 5/e if you wish
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Feb 2008
    Posts
    74
    ok i thought e cant get left in the answer?
    Follow Math Help Forum on Facebook and Google+

  6. #6
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by topaz192 View Post
    ok i thought e cant get left in the answer?
    it can...unless the problem specifically asked you for your answer in decimal
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Junior Member
    Joined
    Feb 2008
    Posts
    74
    yea it did. so how do you get an answer? isnt e^-1?
    Follow Math Help Forum on Facebook and Google+

  8. #8
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by topaz192 View Post
    yea it did. so how do you get an answer? isnt e^-1?
    um, just plug it into your calculator
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Junior Member
    Joined
    Feb 2008
    Posts
    74
    ok! thanks for your time! = )
    Follow Math Help Forum on Facebook and Google+

  10. #10
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by topaz192 View Post
    ok! thanks for your time! = )
    you're welcome
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Help with natural logarithms
    Posted in the Calculus Forum
    Replies: 2
    Last Post: September 19th 2011, 07:13 AM
  2. Natural logarithms
    Posted in the Calculus Forum
    Replies: 4
    Last Post: April 8th 2010, 07:37 AM
  3. Natural logarithms
    Posted in the Pre-Calculus Forum
    Replies: 6
    Last Post: December 22nd 2008, 03:15 PM
  4. Help with natural logarithms?
    Posted in the Algebra Forum
    Replies: 25
    Last Post: March 24th 2008, 06:27 PM
  5. Natural Logarithms...
    Posted in the Algebra Forum
    Replies: 3
    Last Post: January 29th 2007, 04:05 AM

Search Tags


/mathhelpforum @mathhelpforum