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Homework Help: Need help in determining the lim

  1. Nov 28, 2006 #1

    [tex]\lim_{x\rightarrow 4}\frac{x^2 - 3x + 4}{2x^2 - x - 1}[/tex]

    this is lim x ->4 which is the cube root of the whole fraction ^

    Is there any way to answer this because i cant really factor it....
    Last edited: Nov 28, 2006
  2. jcsd
  3. Nov 28, 2006 #2
    Why not just evaluate the limit at [itex] x = 4 [/itex]?
  4. Nov 28, 2006 #3


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    You don't need to factor it. It can easily be factored, since it's a ratio of quadratic polynomials.

  5. Nov 28, 2006 #4
    Assuming f(x) is continuous at f(a) ([tex]\lim_{x \rightarrow a^{+}} f(x) = f(a) =\lim_{x \rightarrow a^{-}} f(x)[/tex]) you can always just plug in a. The only time you would need to factor is if f(x) is not continuous at a or if plugging in a would result in an undefined function (0 in denominator). So yea, as courtigrad said, just substitute x=4. :-)
    Last edited: Nov 28, 2006
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