How many polynomial [math]p(x)[/math] are there such that [math]p(q(x))=q(p(x))[/math] for all polynomial [math]q(x) [/math]?
What are all polynomials [math]p(x)[/math] such that [math]p(q(x))=q(p(x))[/math] for every polynomial [math]q(x)[/math]?