proposition: Lemma dvdr_add_eq a b c : a %| b + c -> (a %| b) = (a %| c).
proof: Proof. by move=> ha; rewrite -[b](addrK c) dvdr_addr // dvdrN. 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