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Math Help - Very simple limit problem

  1. #1
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    Very simple limit problem

    i am not sure if i am posting in the right section anyway i have a problem that is driving me insane, basically i have solve a limit for -4 while the expression is -(9/x+4).

    If i input -4 it will give me -9/0 which is wrong. The tip is that i need to do some algebraical modification to the expression, but i tried everything and it always gives me undefined. I appreciate your time...

    Thank you
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  2. #2
    MHF Contributor Siron's Avatar
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    Re: Very simple limit problem

    If I interpret your question correctly the limit you have to calculate is:
    \lim_{x \to -4} \frac{-9}{x+4}

    Have you ever seen that:
    \lim_{x \to 0} \frac{a}{0}=\pm \infty (a>0 gives +\infty, a<0 gives -\infty)
    ?
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  3. #3
    Super Member TheChaz's Avatar
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    Re: Very simple limit problem

    \lim_{x \to -4} -\frac{9}{x + 4} ?

    That limit doesn't exist.

    Some limits with, for example, "9/0" would be considered "infinity", in the extended sense. But your example tends to +/- infinity, depending on the approach.
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