proposition: Lemma dvdr_add a b c : a %| b -> a %| c -> a %| b + c.
proof: Proof. case/dvdrP=>x bax; case/dvdrP=>y cay. by apply/dvdrP; exists (x + y); rewrite mulrDl bax cay. Qed.
imports: HB(structures) Coq(ssreflect ssrfun ssrbool Arith.Wf_nat) mathcomp(eqtype ssrnat div seq path) mathcomp(ssralg fintype perm tuple choice generic_quotient) mathcomp(matrix bigop zmodp mxalgebra poly) stronglydiscrete