Prove that $SL_2(\mathbb{Z})$ is not perfect
105322
Computing the quotient of SL(2,Z) by its commutator subgroup
138297
Let $G = GL_2\mathbb (R)$. Show that $T$ is a subgroup of $G$
46102
Prove that $2^n +1$ in never a perfect cube
142352
how to prove $G_1$ and $G_2$ aren't isomorphic?
98731
Show that there is no epimorphism from ($\mathbb{Q}$, +) to ($\mathbb{Z}$, +)
68014
Prove that $\mathfrak{su}(2)$ is not isomorphic to $\mathfrak{sl}(2,\mathbb R)$
76501
How can we show that $\mathbb Q$ is not a free $\mathbb Z$-module?
132653
How to show that $\mathfrak{sl}_n(\mathbb{R})$ and $\mathfrak{sl}_n(\mathbb{C})$ are simple?
64130
Prove that $\mathbb{Q}^{\times}$ not isomorphic to $\mathbb{Z}^{n}$
143831
Showing $\mathbb{Q}$ is homeomorphic to $\mathbb{Q}^2$
46687
Elements of $GL_{2}(\mathbb{Z})$ of finite order
151786
Proving that there is no ideal $I$ in $\mathbb{Z}[t]$ such that $\mathbb{Z}[t]/I \cong \mathbb{Q}$
93029
Prove that when $d$ is in $\mathbb{Q} \setminus\mathbb{Z}$, $\mathbb{Z}[\sqrt{d}]$ is not a finitely generated abelian group.
45432
Showing that $f:(0,2\pi]\to S^1$ is not a homeomorphism
46917
How to prove that $GL(n,\mathbb R)$ is not connected subset and open subset of$M_n (\mathbb{R})$
104486
Ideal in $\mathbb Z[x]$ which is not two-generated
63529
How to show that this set is compact in $\ell^2$