 Moreover if either formula_2 or formula_3 is solvable then the Schur–Zassenhaus theorem also states that all complements of formula_2 in G are conjugate.The assumption that either formula_2 or formula_3 is solvable can be dropped as it is always satisfied, but all known proofs of this require the use of the much harder Feit–Thompson theorem.The Schur–Zassenhaus theorem at least partially answers the question