要证 V41∈A()mk[4-,IB]=n 用反证法,若有一个0,使ramk[A-4B<n 彐a≠0 a[4-01B=0→a4-201]=0aB=0 C4B=10B=0 a42B=0B=0 aA"B=0 →a|BAB A-B=0 与 rank[B AB…AB]=n矛盾。i  A() rankA− i I B = n 要证 用反证法，若有一个 0 ，使 rankA− 0 I B  n       0 0 0 0 0 0 0 0 1 1 0 2 0 0 0  = = = = = = − =  − = =   − − B AB A B A B A B AB AB B A I B A I B n n                 rankB AB A B n n = 与  −1 矛盾