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Math Help - Natural Log Rules..Confused

  1. #1
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    Natural Log Rules..Confused

    I am trying to figure out why 2-(1/7)ln(6)+(1/7)ln(4/3) is not 2-(1/7)ln(8). I know if you rearrange it as 2+(1/7)ln(4/3)-(1/7)ln(6) you get 2+(1/7)ln(2/9) which is the correct answer...which is using the lnx-lny=ln(x/y) rule. However how come you cannot apply the lnx+lny=ln(xy) rule for 2-(1/7)ln(6)+(1/7)ln(4/3).

    thanks
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  2. #2
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    2-(1/7)ln(6)+(1/7)ln(4/3) is not 2-(1/7)ln(8).
    because it is equal to your answer if it is written as
    2-[(1/7)ln(6)+(1/7)ln(4/3)]
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  3. #3
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    The minus must be distributed.
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  4. #4
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    Smile

    Quote Originally Posted by bfpri View Post
    . However how come you cannot apply the lnx+lny=ln(xy) rule for 2-(1/7)ln(6)+(1/7)ln(4/3).

    thanks
    yes you can
    2-(1/7)ln(6)+(1/7)ln(4/3) = 2-1/7(ln(6) - ln(4/3)) = 2-1/7ln(9/2)
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  5. #5
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    Duh..thanks guys!
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