Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
Drexel University or The Math Forum.



Questions regarding Descartes's Rule of Signs
Posted:
Feb 15, 2005 4:48 PM


Hello. I'm working with Descartes's rule of signs currently and I understand it, however this equation doesn't follow the rule. Are there exceptions?
 Find all real zeros f(x) = 2x^3 + 3x^2  1 f(x) = 2(x)^3 + 3(x)^2  1
In this equation I see 1 sign change. Using Descartes's rule this would show 1 or 0 real zero's with no negative zero's.
However! There is 1 positive zero (1/2) and 1 negative zero (1).
Can somebody please explain to me what I am doing wrong with the rule?
Thanks! Aaron
 submissions: post to k12.ed.math or email to k12math@k12groups.org private email to the k12.ed.math moderator: kemmoderator@k12groups.org newsgroup website: http://www.thinkspot.net/k12math/ newsgroup charter: http://www.thinkspot.net/k12math/charter.html



