Show a sequence of R-modules and R-homomorphisms is exact.
7441
Hom is a left-exact functor
141149
Proof some module is direct sum by its submodules.
99567
Proving that an inverse ring homomorphism of an ideal is an ideal?
97608
Showing a Ring of endomorphisms is isomorphic to a Ring
121465
$R[x]$ has a subring isomorphic to $R$.
18343
Counting homomorphisms between $\Bbb Z$ and $\Bbb Z_n$ and also between $\Bbb Z_n$ and $\Bbb Q$
9562
Proving that surjective endomorphisms of Noetherian modules are isomorphisms and a semi-simple and noetherian module is artinian.
73825
Every $R$-module is a quotient of a free module
40678
Image of an ideal under a surjective ring homomorphism is an ideal
76040
Show that the Euler characteristic of a chain complex is equal to the Euler characteristic of its homology
129858
"Almost" ring homomorphism
144122
A problem about an $R$-module that is both injective and projective.
140340
Left and right R-modules
132300
Dimensions of vector spaces in an exact sequence
57732
Rings of fractions and homomorphisms
51695
Finding all homomorphisms between $\mathbb{Z}/m\mathbb{Z}$ and $\mathbb{Z}/n\mathbb{Z}$
83710
Order of a homomorphism of groups