proposition: Lemma eqrMn2r n x y : (x *+ n == y *+ n) = (n == 0)%N || (x == y).
proof: Proof. by rewrite !(@eq_le _ R) !lerMn2r -orb_andr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)