proposition: Lemma mulrnAC x m n : x *+ m *+ n = x *+ n *+ m.
proof: Proof. by rewrite -!mulrnA mulnC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)