$\Bbb Z[\sqrt{-5}]$ is not a PID
36862
A question about proving that there is no greatest common divisor
17991
Nonconstant polynomials do not generate maximal ideals in $\mathbb Z[x]$
125668
A proof that BS(1,2) is not polycyclic
53331
$\mathbb{Q}(\sqrt2, \sqrt3)$ is not isomorphic to $\mathbb{Q}(\sqrt[4]2)$
58009
How to show that $\mathbb Q(\sqrt 2)$ is not field isomorphic to $\mathbb Q(\sqrt 3).$
158502
Showing $\sin(\bar{z})$ is not analytic at any point of $\mathbb{C}$
127237
Let $I = \{a +ib \in \Bbb Z[i] : a$ and $b$ are both multiple of $5\}$.
31451
Proving a subring of $\mathbb{Q}$ containing $\mathbb{Z}$ is a PID
77735
When $\Bbb Z_n$ is a domain. Counterexample to $ab \equiv 0 \Rightarrow a\equiv 0$ or $b\equiv 0\pmod n$
121845
Quotient of polynomials, PID but not Euclidean domain?
44496
Norm $N$ on $\Bbb Z[\sqrt d]$ is multiplicative, $N(x)$ prime $\Rightarrow x$ irreducible
128732
$\mathbb Z_{p^n}$ is not the direct product of any family of its proper subgroups
146470
Show $\mathbb{Z}[\sqrt{6}]$ is a Euclidean domain
40041
Proof of Non-Ordering of Complex Field
24413
Why is $\mathbb{Z}[\sqrt{-n}], n\ge 3$ not a UFD?
95669
Solutions of $|z| = z^5$ in $\Bbb{C}$?
59261
If $n\in\Bbb Z^+$ is not a square, prove exist infinitely many primes $p$ such that $\left(\frac{n}{p}\right)=-1$.