Question 50
Find all non-constant polynomials $P(x)$ with integer coefficients such that for each $n$ the polynomial $P^n(x)$ only has integer roots.
(Where $P^n(x)$ means the $n^{\text{th}}$ fold composition of $P(x)$ with itself.)
(Where $P^n(x)$ means the $n^{\text{th}}$ fold composition of $P(x)$ with itself.)