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Discussion: Traffic Jam Applet tool
Topic: evaluating -x^c
Related Item: http://mathforum.org/mathtools/tool/10/


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Subject:   evaluating -x^c
Author: Bethany
Date: Sep 27 2004
I'm interested in how most K-12 teachers expect this expression to be
evaluated...  as (-x)^c or as -(x^c).  Using the TI83 there seems to be some
inconsistency between graphing and evaluating.  

For instance, if I type in the expression -3.8^2.1 I get a response to be
-16.502...  Yet when I try to graph x^2.1 the graph is only defined for
positive x.

So it seems that the calculator when evaluating the expression takes 3.8^2.1
then negates it.  But when it graphs it tries to evaluate (-3.8)^2.1 which of
course _is_ undefined.

Also of interest to note is in MS Excel, typing that expression yields an
error.

So really, what do you as teachers expect that expression to evaluate to?



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