Additive identity in a semiring need not be multiplicative annihilator.
94203
Examples for almost-semirings without absorbing zero
69046
Proof of $\mathbb{Q}$ is not cyclic
129693
An interesting problem with "decomposing" natural numbers.
55026
$\mathbb{Q}[X,Y]/(Y^2-X^3)$ is not a UFD
128043
$A^n=0$ for $A$ nilpotent without the use of minimal polynomial
62635
Prove that the additive group $ℚ$ is not isomorphic with the multiplicative group $ℚ^*$.
153100
A counterexample to "$k\mid n$ if and only if $k\mid n^2$"
51593
Every finite commutative ring with no zero divisors contains a multiplicative identity?
74139
Subrings of integral domains have the same identity element.
132386
Show that $(\mathbb{Q}^*,\cdot)$ and $(\mathbb{R}^*,\cdot)$ aren't cyclic
3902
Does $k+\aleph_0=\mathfrak{c}$ imply $k=\mathfrak{c}$ without the Axiom of Choice?
108955
Showing $(\mathbb{Q},+)$ is not isomorphic to $(\mathbb{R},+)$
158426
Proving lemma about centrality of idempotent elements in a Ring with no nilpotent elements.
75970
$\mathbb Z[1/2]$ is not finitely generated?
86015
$\mathbb Q[x]/(x^2+1)$ is not isomorphic to $\mathbb Q[x]/(x^2+2)$
80211
Annihilator of quotient module M/IM
155604
Show that $k[x,y]/(xy-1)$ is not isomorphic to a polynomial ring in one variable.