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Derivative test

  1. Oct 21, 2007 #1
    1. According to the First Derivative Test for local extrema, if f' doesn't change sign at c, then f has no local extreme value at c. But for a question on my book, f(x)=(4-x^2)^(-1/2), the critical point is 0, but i think it doesn't have local extreme because the derivative doesn't change sign ,but my book says it has minimum value at x=0.
    Thanks for help.
  2. jcsd
  3. Oct 21, 2007 #2


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    Can you write out the calculations leading you to conclude that the derivative doesn't change sign at x = 0?
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