Descartes' Rule of Signs
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Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny  
A discussion by Scott Brodie of the basis of the attribution to Descartes of the proposition now known as Descartes' Rule of Signs: The number of positive roots of a polynomial with real coefficients is equal to the number of "changes of sign" in the list of coefficients, or is less than this number by a multiple of 2. With a simple proof by induction, using Bolzano's Theorem.  


Levels:  High School (912), College 
Languages:  English 
Math Topics:  Polynomials 
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