proposition: Lemma expfzDr x m n : x != 0 -> x ^ (m + n) = x ^ m * x ^ n.
proof: Proof. by move=> hx; rewrite exprzDr ?unitfE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)