Abstract
23.1 Galois' criterion 23.2 Composition series, Jordan-Hölder theorem 23.3 Solving cubics by radicals 23.4 Worked examples Around 1800, Ruffini sketched a proof, completed by Abel, that the general quintic equation is not solvable in radicals, by contrast to cubics and quartics whose solutions by radicals were found in the Italian renaissance, not to… (More)