Comment by gus_massa

I teach math in the first year of the university in Argentina. This method is well known since many years, probably like 20 or more. It's more popular in foreign students (Brazil? Peru?) that have some kind of standardized test with many short questions. The local students use the classic formula (sometimes unsuccessfully).

It's a nice trick for equations with small nice numbers, that are common in math tests. But it fails spectacularly when you try to apply it to physics or chemistry problems that have decimals and nasty irrational solutions.

I don't like it, because it use that mathematicians like to put only nice numbers, even in topics like linear algebra or calculus that are about the real numbers.

But I don't mind something like this method for advanced math courses like Galois Theory, where the polynomials have integer or rational coefficients, and you can use the Gauss method https://en.wikipedia.org/wiki/Rational_root_theorem to find all the rational roots, that is quite similar to this "new" method.