Finding a subring of $M(2,\mathbb{Q})$ which is isomorphic to a) $\mathbb{Q}\times \mathbb{Q}$ b)$\mathbb{Q}$ c)$\frac{\mathbb{Q}[x]}{(x^2)}$.
136389
Finding an isomorphic subring of matrices
120035
Pattern in Isomorphisms between $\mathbb Z_m \times \mathbb Z_n$ and $\mathbb Z_{mn}$
154754
Is $O_n$ isomorphic to $SO_n \times \{\pm I\}$?
146334
Are there fields $F$ such that the rings $F[x]/(x^2)$ and $F[x]/(x^2-1)$ are isomorphic?
139162
Complex number isomorphic to certain $2\times 2$ matrices?
127198
What is $\mathbb{C}^{Aut(\mathbb{C}/\mathbb{Q})}$?
121823
Number of subrings of a Field
55900
Is there a ring homomorphism $M_2(\mathbb Z)\to \mathbb Z$?
145221
Ring isomorphism (polynomials in one variable)
20199
Find a surjective function $f:\mathbb{N}\to \mathbb{Q}$
51695
Finding all homomorphisms between $\mathbb{Z}/m\mathbb{Z}$ and $\mathbb{Z}/n\mathbb{Z}$
109596
Isomorphism from $\mathrm{Aut}(\mathbb{Z}/2\mathbb{Z}\times \mathbb{Z}/2\mathbb{Z})$ to $S_3$
39642
Efficient way to find $[\mathbb{Q}(\sqrt{5}, \sqrt{3}, \sqrt{2}): \mathbb{Q}(\sqrt{3}, \sqrt{2})]$
120183
Prove that $S_3\times\mathbb{Z}_2$ is isomorphic to $D_6$
9140
Show $\operatorname{Aut}(C_2 \times C_2)$ is isomorphic to $S_3=D_6$
55393
Existence of a group isomorphism between $(\mathbb K,+)$ and $(\mathbb K^\times,\cdot)$
53331
$\mathbb{Q}(\sqrt2, \sqrt3)$ is not isomorphic to $\mathbb{Q}(\sqrt[4]2)$