WEBVTT
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we want to find the domain of this function and
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remember that the domain is the set of rial number
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inputs that would yield rial number outputs. And when
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you're looking at a rational function like this, you
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want to focus on the denominator. Remember that division
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by zero is undefined, and so the denominator cannot
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be equal to zero. So let's figure out what
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numbers would make the denominator equal. Zero. If
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X squared minus nine was equal to zero, then
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X squared would be equal to nine and X would
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be equal to plus or minus three. So we're
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saying that those numbers cannot be in the domain and
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everything else can. So we have different ways of
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expressing the domain. One way is to use interval
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notation so we would have all the numbers from negative
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infinity to negative three round brackets showing that you're not
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including it union, Which means or and then all
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the numbers from negative 3 to 3 again round Brackett
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, showing that you're not including it and then union
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, which means or again, and then the interval
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from three to infinity. So that's one way of
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saying all real numbers except X equals three and X
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equals negative three