{tag=Quadratic Diophantine equation}

TODO is it or is not:
* https://mathoverflow.net/questions/207482/algorithmic-un-solvability-of-diophantine-equations-of-given-degree-with-given
* https://math.stackexchange.com/questions/181380/second-degree-diophantine-equations
* https://mathoverflow.net/questions/142938/is-there-an-algorithm-to-solve-quadratic-diophantine-equations
* https://math.stackexchange.com/questions/798609/is-there-any-solution-to-this-quadratic-diophantine-equation


Hilbert's tenth problem is decidable for quadratic equations