Show that $I_2 = (2, 1+ \sqrt{-5})$ is not a principal ideal
78351
Why is $(2, 1+\sqrt{-5})$ not principal?
154845
Irreducible elements in  $\mathbb{Z}[\sqrt{-2}]$ and is it a Euclidean domain?
12927
$A^2+B^2=AB$ and $BA-AB$ is non-singular
108955
Showing $(\mathbb{Q},+)$ is not isomorphic to $(\mathbb{R},+)$
120181
The ideal generated by $2$ and $ x$ in $\mathbb{Z}[x]$
5526
Prove that $ℤ[i]^*= \{1,-1,i,-i\}$
41872
Show that $\mathbb{R}^2$ is not homeomorphic to $\mathbb{R}^2 \setminus\{(0,0)\}$
24351
The ring $\Bbb Z\left [\frac{-1+\sqrt{-19}}{2}\right ]$ is not a Euclidean domain
55077
prove that $2\sqrt5 +\sqrt{11}$ is irrational
86816
Example of two prime ideals whose intersection of the squares not equal to the square of the intersection
133561
show that if $K$ is a field then $K[x]$ is principal
69373
Prove that $(0)$ is a radical ideal in $\mathbb{Z}/n\mathbb{Z}$ iff $n$ is square free
67605
Different proof that $\sqrt{2}$ is irrational
129302
Proving whether ideals are prime in $\mathbb{Z}[\sqrt{-5}]$
138752
Prove the Radical of an Ideal is an Ideal
88429
Prove $\sqrt{2} + \sqrt{5}$ is irrational
78873
How to show that the monomials are not a Schauder basis for $C[0,1]$