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Re: [apcalculus] Double Derivatives
Posted:
Oct 23, 2012 8:52 PM


NOTE: This apcalculus EDG will be closing in the next few weeks. Please sign up for the new AP Calculus Teacher Community Forum at https://apcommunity.collegeboard.org/gettingstarted and post messages there.  Debbie, Not always. In order to determine whether or not the xcoordinate is the xcoordinate of a POI you need to check the sign of the second derivative on either side of that xcoordinate. My students often ask me that question. That is when we examine the function f(x) = x^4. f " (x) = 0 @ x = 0, but the concavity does not change at x = 0, and therefore not a POI. We then go back to the first derative test and see that the first derivative changes signs from negative to positive at x = 0, thus giving us a relative min of 0 at x = 0. I hope that helps , Greg Field Grayson High School Loganville, GA
________________________________ From: Debbie Bricker <DBricker@cathedralcatholic.org> To: AP Calculus <apcalculus@lyris.collegeboard.com> Sent: Tuesday, October 23, 2012 5:12 PM Subject: [apcalculus] Double Derivatives
Double Derivatives NOTE: This apcalculus EDG will be closing in the next few weeks. Please sign up for the new AP Calculus Teacher Community Forum at https://apcommunity.collegeboard.org/gettingstarted and post messages there.  In using the second derivative test for extrema, you may get the second derivative to equal zero when plugging in a critical number and the test then fails. Will this point then be a POI?
Debbie To search the list archives for previous posts go to http://lyris.collegeboard.com/read/?forum=apcalculus  To search the list archives for previous posts go to http://lyris.collegeboard.com/read/?forum=apcalculus



