proposition: Fact mulrzA_C m n x : (x *~ n) *~ m = x *~ (m * n).
proof: Proof. elim: m=> [|m _|m _]; elim: n=> [|n _|n _]; rewrite /intmul //=; rewrite ?(muln0, mulr0n, mul0rn, oppr0, mulNrn, opprK) //; do ?by rewrite mulnC mulrnA. * by rewrite -mulrnA mulnC. * by rewrite -mulrnA. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)