Possible Duplicate:
Enestrom-Kakeya Theorem
Suppose that $0<a_0\leq a_1\leq\cdots\leq a_n$, then prove that the complex polynomial $$P_n(z)=a_0z^n+a_1z^{n-1}+\cdots+a_{n-1}z+a_n$$ cannot have a root in the unit disc, i.e., such that $|z|<1$.
Possible Duplicate:
Enestrom-Kakeya Theorem
Suppose that $0<a_0\leq a_1\leq\cdots\leq a_n$, then prove that the complex polynomial $$P_n(z)=a_0z^n+a_1z^{n-1}+\cdots+a_{n-1}z+a_n$$ cannot have a root in the unit disc, i.e., such that $|z|<1$.