How to prove a cube minus a cube is never a cube (in whole numbers)
136894
Reference request: Clean proof of Fermat's last theorem for $n=3$.
103146
Proof that the Rubik’s Cube group is 2-generated
79056
Prove that $\mathbb Z^n$ is not isomorphic to $\mathbb Z^m$ for $m\neq n$
107395
If the sum of $n$ cubes is zero, then the sum must be no larger than $\frac n3$.
109858
How could a statement be true without proof?
123458
Prove $( \lnot C \implies \lnot B) \implies (B \implies C)$ without the Deduction Theorem
151637
How do we prove that this set is not manifold?
20593
Show that if $a \neq b$ and a and b are positive then $\frac{a}{b}+\frac{b}{a}$ is never an integer
70576
Elementary proof that $\mathbb{R}^n$ is not homeomorphic to $\mathbb{R}^m$
110608
What is $\,a\bmod 63\,$ if $\,a\,$ is both a square and a cube?
18160
How to show that the group of nonzero real numbers under multiplication is not isomorphic to the group of real numbers under addition?
69606
How to prove rank(A+) is no more than rank(A)?
25874
Showing that a certain map is not flat by explicit counterexample
99631
Prove/Disprove: Find $a\in S_4$ that is not a power of $b$ such that $ab=ba$ while $b=(123)$
57250
Proving that the sum and difference of two squares (not equal to zero) can't both be squares.
89452
Proof about Graph with no triangle
73248
Prove that $\mathbb{R^*}$, the set of all real numbers except $0$, is not a cyclic group