## Precalculus (6th Edition) Blitzer

Let $f\left( x \right)={{a}_{n}}{{x}^{n}}+{{a}_{n-1}}{{x}^{n-1}}+\cdot \cdot \cdot +{{a}_{1}}x+{{a}_{0}}$ be a polynomial of degree $n$. The number of real roots, positive roots or negative roots of a polynomial of degree $n$ can be found out through Descartes' rule. According to the Descartes' rule, the number of positive real zeros of a polynomial function is equal to the number of polynomial function $f\left( x \right)$ sign changes or less than the number of sign changes. The number of negative real zeros of a polynomial function is equal to the number of polynomial function $f\left( -x \right)$ sign changes or less than the number of sign changes. So, the given statement is true.