proposition: Lemma lte_ndivl_mull r x y : (r < 0)%R -> (x < r^-1%:E * y) = (y < r%:E * x).
proof: Proof. by move=> r0; rewrite muleC lte_ndivl_mulr// muleC. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed