proposition: Lemma lregMl (a b: R) : lreg (a * b) -> lreg b.
proof: Proof. by move=> rab c c' eq_bc; apply/rab; rewrite -!mulrA eq_bc. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype finfun perm matrix bigop zmodp mxalgebra) mathcomp(choice poly polydiv mxpoly binomial)