西安毛子科技大学XIDIANUNIVERSITY对A作分块下面考虑n级矩阵A=(ai)nxnaanBα =(an1,an2,"",an,n-1)an-2,nn-1.nβE0A山0-αA-βann(B,A)B,ββ7AB,100am-αA-βann-αA-"βR为上三角形.为上三角形． 对A作分块 1 1 1 2 , 1 2 , 1 , , , ( , , , ) n n n n n nn n n n n a A A a a a a a a     − − −       = = =           则 1 1 1 1 1 1 0 1 nn 0 nn E A A A a a A       − −         =     −   −   1 1 1 1 1 1 1 1 1 0 0 1 0 0 nn nn B A B A B a A a A       − −           =   − −     n ( ) . 下面考虑 级矩阵 A a = ij n n