Here's the question you clicked on:
DeadShot
How do I explain how the Rational Root Theorem and Descartes' Rule of Signs are used to find the zeros of a polynomial function?
Descartes' Rule of Signs will not tell you where the polynomial's zeroes are (you'll need to use the Rational Roots Test and synthetic division, or draw a graph, to actually find the roots), but the Rule will tell you how many roots you can expect. Sescartes rule of signs tells you how many zeros you will have and which will be negative and which positive. Rational root therom tells the possible zeros it could be.