Proving why $\Bbb Z_{4} \rightarrow \Bbb Z_{6} \text{ given by } f(\overline x) = [2x+1] $ is not a function.
114219
The map $f:\mathbb{Z}_3 \to \mathbb{Z}_6$ given by $f(x + 3\mathbb{Z}) = x + 6\mathbb{Z}$ is not well-defined
139288
Formal proof that $e^x$ is not algebraic
112933
Show that $Z\times Z$ is not cyclic...
18484
Show that $k[x,y,z]/(xz-y^2)$ is not a UFD.
30781
Why the representation in the form of $Z'X(X'X)^{-1}X'Z$ can not be simplified into $Z'Z$
147429
Set of points in $\mathbb{C}$ s.t. $z^{n-1} = \overline z$
155266
Is $\exp:\overline{\mathbb{M}}_n\to\mathbb{M}_n$ injective?
91947
Proof of $ f:I_n \rightarrow I_m \Rightarrow n = m$
66020
What is $\mathbb Z[[t]]$? What are the double brackets?
126989
Prove that $g(z)=\overline{f(z)}$ is complex diﬀerentiable at $a$ if and only if $f'(a) = 0$.
57166
Showing that $\Bbb R[x] / \langle x^2 + 1 \rangle$ is isomorphic to $\Bbb C$ question
14994
Showing a function $f$ cannot be surjective
79056
Prove that $\mathbb Z^n$ is not isomorphic to $\mathbb Z^m$ for $m\neq n$
121729
Prove without using graphing calculators that $f: \mathbb R\to \mathbb R,\,f(x)=x+\sin x$ is both one-to-one, onto (bijective) function.
132193
Why $\Bbb Z$ = (integers) is an integral domain?
55026
$\mathbb{Q}[X,Y]/(Y^2-X^3)$ is not a UFD
85586
Proving $\mathbb{Q}$ isn't homeomorphic to $\mathbb{Z}$