proposition: Lemma leR_add2r x y z : y + x <= z + x <-> y <= z.
proof: Proof. by rewrite -!(addRC x); apply: leR_add2l. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div order) mathcomp(ssralg ssrnum ssrint rat intdiv) Coq(Morphisms Setoid) fourcolor(real realsyntax)