'Non-example' to the Lagrange theorem.
14611
$A_4$ has no subgroup of order $6$?
127688
Example where convergence in mean does not imply convergence in quadratic mean
20614
Example of a function such that $\varphi\left(\frac{x+y}{2}\right)\leq \frac{\varphi(x)+\varphi(y)}{2}$ but $\varphi$ is not convex
146024
Help with counter-example on uniformly convergence.
109666
Example where partial derivatives commute but are not continuous.
156839
Functions Which are non differentiable on a Given Set.
150961
An example for a homomorphism that is not an automorphism
83778
An incorrect proof by exhaustion
42384
Сanonical form of a quadratic form by Lagrange's method
144316
counterexample to Abel's theorem
67383
Prove that $G'$ is not planar.
117990
Derivation of the method of Lagrange multipliers?
56446
A kind of converse of Lagrange's Theorem
106716
The sum of square roots of non-perfect squares is never integer
38299
Why do Lagrange Multipliers work?
123132
Counterexample for a non-measurable function?
47937
Example of a Borel set that is neither $F_\sigma$ nor $G_\delta$