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Topic: [ap-calculus] TI-89 question
Replies: 1   Last Post: Sep 27, 2012 7:02 PM

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Jon Stark

Posts: 914
Registered: 6/10/06
RE: [ap-calculus] TI-89 question
Posted: Sep 27, 2012 7:02 PM
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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 var-link, find " x EXPR 4" in the list, and delete it before invoking the derivative command.

Jewel Filipovich wrote:
I have used a TI-89 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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