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Use the properties of logarithma to xpand the logarithmic function

  1. Nov 19, 2009 #1
    1. The problem statement, all variables and given/known data
    Use the properties of logarithma to xpand the logarithmic function ln[(x2+1)(x-1)]


    2. Relevant equations



    3. The attempt at a solution
    [ln x2+ln 1]+[ln x-ln 1]
    2 ln x+ln x
     
  2. jcsd
  3. Nov 19, 2009 #2
    the first step makes sense: [tex]ln[(x^2+1)(x-1)]=ln(x^2+1)+ln(x-1)[/tex]

    but then you continued: [tex]ln(x^2+1)=ln(x^2)+ln(1)[/tex]

    You can't do that, but you can do something else to the [tex]x^2+1[/tex]...
     
  4. Nov 19, 2009 #3

    Mark44

    Staff: Mentor

    Is the something else you're thinking about factoring x^2 + 1?
     
  5. Nov 20, 2009 #4
    I just realized I was stupidly thinking of [tex]x^2-1[/tex] not [tex]x^2+1[/tex]. You can't really factor that term unless you go into imaginary numbers.
     
  6. Nov 20, 2009 #5

    Mark44

    Staff: Mentor

    That's what I thought you might be thinking.
     
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