Casus irreducibilis, which is Latin for "the irreducible case", is the situation in which an irreducible cubic polynomial has all real roots. In order to obtain the roots by radicals in such cases, it is always necessary to express the roots using complex-valued numbers.

status | proved proof date | 1891 (135 years ago) prover | Otto Hölder additional people involved | Gerolamo Cardano | Niccolò Tartaglia

solved mathematics problems | mathematics theorems