Calculator test

[dm319]

From Wikipedia:

In Hellenistic Egypt, the Greek mathematician Diophantus in the 3rd century AD referred to an equation that was equivalent to \[4 x + 20 = 4\] (which has a negative solution) in Arithmetica, saying that the equation was absurd.[24] For this reason Greek geometers were able to solve geometrically all forms of the quadratic equation which give positive roots; while they could take no account of others.

Also from Wikipedia, casus irreducibilis:

It shows that many algebraic numbers are real-valued but cannot be expressed in radicals without introducing complex numbers. The most notable occurrence of casus irreducibilis is in the case of cubic polynomials that have three real roots, which was proven by Pierre Wantzel in 1843.

As my maths isn't good enough, I can at least extrapolate conceptionally from negative numbers to i.