行列式可由Laplace展开定理,按第n+1,n+2,...,n+m行展开
|D| = |A||B| (-1)^t
t = n+1,n+2,...,n+m + 1+2+...+m = mn + 2(1+2+..+m)
所以 |D| = |A||B| (-1)^mn
D 的逆 = ( O,B逆 ; A逆,- A逆CB逆 )