若 Amxn =(A,A,"",A,),D= diag(a,2,..",an)元则 A,D=(A,A福=(a,A,A,..,a,An)84.5矩阵的分块§4.5 矩阵的分块 1 1 2 2 ( , , , ) =    A A A n n 1 2 1 2 ( , , , ), ( , , , ) ② 若 A A A A D diag m n n n  = =    1 2 1 2 ( , , ) m n n n A D A A A                 则 = O O