proposition: Lemma lerD2r x : {mono +%R^~ x : y z / y <= z}.
proof: Proof. by move=> y z; rewrite ![_ + x]addrC lerD2l. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)