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Math Help - Restrictions on Variables of Logs

  1. #1
    Senior Member
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    Nov 2008
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    Restrictions on Variables of Logs

    Hi there

    I just have a quick question regarding this question:

    Simplify. State any restrictions on the variables.

    log(x^2+7x+12)-log(x^2-9)

    my answer is log[(x+4)/(x-3)] which is correct. However, for the restrictions, I believe that they are: x>3 and x<-4.. But the back of the book says only x>3.

    When I plug in x<-4 any number such as x=-5 the expression is defined. So.. my question, is the back of the book wrong? Are there 2 restrictions and not one?

    Thanks, please explain your answer fully.
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  2. #2
    Super Member
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    May 2009
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    Edit: never mind, I totally misread the question. Grr...


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