grandes-ecoles 2025 Q5

grandes-ecoles · France · mines-ponts-maths1__pc Roots of polynomials Reciprocal and antireciprocal polynomial properties
Let $R$ be a non-constant polynomial of $\mathbf{C}[X]$ having the following property: Every root $a$ of $R$ is nonzero and $\frac{1}{a}$ is a root of $R$ with the same multiplicity as $a$.
Deduce that $R$ is reciprocal or antireciprocal.
Let $R$ be a non-constant polynomial of $\mathbf{C}[X]$ having the following property: Every root $a$ of $R$ is nonzero and $\frac{1}{a}$ is a root of $R$ with the same multiplicity as $a$.

Deduce that $R$ is reciprocal or antireciprocal.