Interactive Mathematics
Interactive Mathematics: Polynomial Functions and Equations
Want to find the roots of a polynomial function? Learn how, using several methods in this tutorial. Graphing and Scientific Notebook are used on the main page. Click on the "Dinosaur Method" link at the bottom of the page to see the...
Purple Math
Purplemath: Finding Quadratics From Their Zeroes
Students often have difficulty "working backwards" from the solution of a problem to its original question. Finding a polynomial, given its roots, is an example of a "working backwards" problem. Here are several examples using different...
Wolfram Research
Wolfram Math World: Descartes' Sign Rule
This page gives a good overview of Descartes' Sign Rule, a "method of determining the maximum number of positive and negative real roots of a polynomial."