set Pm = Polynom-Ring (n,L);
thus
Polynom-Ring (n,L) is well-unital
by Lm1; Polynom-Ring (n,L) is right-distributive
let x, y, z be Element of (Polynom-Ring (n,L)); VECTSP_1:def 2 x * (y + z) = (x * y) + (x * z)
reconsider p = x, q = y, r = z as Polynomial of n,L by Def11;
A1:
( x * y = p *' q & x * z = p *' r )
by Def11;
y + z = q + r
by Def11;
hence x * (y + z) =
p *' (q + r)
by Def11
.=
(p *' q) + (p *' r)
by Th26
.=
(x * y) + (x * z)
by A1, Def11
;
verum