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Math Help - domain question

  1. #1
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    domain question

    Hey everybody, I just had a quick question about domain and how to write them in interval notation (I think that's what it's called).

    So I have one problem,
    <br />
f(x)=\frac {2x-5}{x^2-5x-6}<br />

    For this problem I got the domain:
    <br />
(-\infty, -1) \cup (-1, 6) \cup (6, \infty)<br />

    For the other problem,
    <br />
f(x)= \frac {2x-7}{x^2-x-12}<br />

    with this domain:
    <br />
(-\infty, -3) \cup (4, \infty)<br />

    My question is this: why are there two 'U' in the first domain but not the second one? Have I just written the second one incorrectly? Any help is appreciated!
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  2. #2
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    Quote Originally Posted by sciencefun View Post
    in the second domain function,you forgot to include:
    (-3,4) as your domain.
    Ok I had a feeling I had that second one wrong. So would the middle part always be included in every domain?
    Last edited by mr fantastic; June 2nd 2010 at 06:13 AM.
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  3. #3
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    Quote Originally Posted by kevin11 View Post
    Ok I had a feeling I had that second one wrong. So would the middle part always be included in every domain?
    The domain is all real numbers except for values of x such that x^2 - x - 12 = 0. You should think about why.
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