proposition: Lemma sumrN I r P (F : I -> V) : (\sum_(i <- r | P i) - F i = - (\sum_(i <- r | P i) F i)).
proof: Proof. by rewrite (big_morph _ opprD oppr0). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)