proposition: Lemma fgscaleDr c D1 D2 : c *:F (D1 + D2) = c *:F D1 + c *:F D2.
proof: Proof. by apply/eqP/freeg_eqP=> x; rewrite !(coeffD, coeff_fgscale) mulrDr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order generic_quotient) mathcomp(ssralg ssrnum ssrint)