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Need help with math limit problem

  1. Sep 24, 2005 #1
    i have done part of the work
    but i got stuck here

    what is
    lim f(x) = lim ln [(x + 2)/(x - 1)] =???
    x→-2- x→-2-

    how do u solve for this?
  2. jcsd
  3. Sep 24, 2005 #2


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    Homework Helper

    What is:
    [tex]\lim_{x \rightarrow -2 ^ -} \frac{x + 2}{x - 1}[/tex]? Note that the numerator tends to 0, while the denominator tends to -3.
    Then what can you say about:
    [tex]\lim_{x \rightarrow 0 ^ +} \ln x[/tex]?
    Viet Dao,
  4. Sep 24, 2005 #3
    that would be -infinity??

    how about
    lim f(x) = lim ln [(x + 2)/(x - 1)] =???
    x→-2+ x→-2+
  5. Sep 25, 2005 #4


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    Obviously, the numerator and denominator will separately approach the same values, so the ratio will also approach the same value. However, notice that in this case, the numerator will always be positive while the denominator will be negative. What does that tell you about the ratio? And what happens when you take the natural log of such a quantity? So, what can you say about the function when you try to take this limit?
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