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Math Help - Plugging in number

  1. #1
    Junior Member
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    Plugging in number

    my teacher for our first homework assignment gave us half answers, but i cant get the correct answer for this:

    (x^2 - 14x - 51)/(x^2 - 4x - 21) when you plug in -3 is equal to what?

    my math teacher says 2 is the answer, but i always get (9 + 42 - 51) / (9+12 -21) = (51-51) / (21-21) = 0/0

    is my math teacher wrong? or what am i doing incorrectly?
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  2. #2
    Senior Member vincisonfire's Avatar
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    This simply means that the function is not defined at the point x=-3. So if you're asked what is f(-3) just answer it doesn't exist or it is not defined.
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