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Homework Help: Range Of Function

  1. Mar 26, 2008 #1
    Let f(x)= ln(-x^2+x+6)

    Find the range of f(x). Use f'(x) to support your answer.

    Attempt at a solution:

    Find the max. value of the range is easy. I found the derivative and set it equal to zero. My REAL PROBLEM is finding the minimum value of the range.

    The function's domain must be between -2 and 3 becus you cannot take the natural lg of a negative number or zero.
    SO, as f(x) approaches, 3 or -2, does it approach negative infinity??
    Am I right when I say its lower range is negative infinity?? HELP!
  2. jcsd
  3. Mar 26, 2008 #2


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    Science Advisor
    Homework Helper

    As x approaches -2 from above or 3 from below, then -x^2+x+6 approaches 0 from above. So yes, you are right.
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