proposition: Lemma summablebDr (S1 S2 : T -> R) : summable S2 -> `[< summable (S1 \+ S2) >] = `[< summable S1 >].
proof: Proof. move=> sm1; rewrite (@eq_summableb _ _ (S2 \+ S1)) ?summablebDl //. by move=> x /=; rewrite addrC. Qed.
imports: mathcomp(all_ssreflect all_algebra) mathcomp.classical(boolp) xfinmap ereal reals discrete realseq mathcomp.classical(classical_sets functions mathcomp_extra) topology