因为 AA' = E所以 |A+E| = |A+AA'| = |A(E+A')|= |A| |E+A'|= |A| |(E+A)'|= |A| |E+A|= - |A+E|所以 2|A+E| = 0所以 |A+E| = 0.所以 A+E 不可逆.
