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RE: [apcalculus] TI89 question
Posted:
Sep 27, 2012 7:02 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.  If the value of 0 has been stored as the variable x in a previous computation, program, or graphing operation (even inadvertently), the derivative will be evaluated at x=0 instead of in general form. That will yield 3 as the answer. To see this in action, type 1 (sto>) x, and then ask for the derivative again, and you'll get 7.
To prevent this, go to 2nd varlink, find " x EXPR 4" in the list, and delete it before invoking the derivative command.
Jewel Filipovich wrote: I have used a TI89 for a long while and never come across this problem. One of my student's calculator: when you ask it to determine a derivative entered as d(2x^2 +3x,x), I get an answer of just 3, rather than 4x + 3. It does not matter if you put multiplication signs in between either. Any thoughts??
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