English
If R is a commutative ring and A is a nonunital commutative ring with Module structure, Unitization(R, A) is a commutative ring.
Русский
Если R — коммутативное кольцо, а A — коммутативное немонолитное кольцо, Unitization(R, A) является коммутативным кольцом.
LaTeX
$$$\text{CommRing}(\mathrm{Unitization}(R,A)).$$$
Lean4
instance instCommRing [CommRing R] [NonUnitalCommRing A] [Module R A] [IsScalarTower R A A] [SMulCommClass R A A] :
CommRing (Unitization R A) :=
{ Unitization.instAddCommGroup, Unitization.instCommSemiring with }