2矩阵的加减运算 设A B=l6 h×n nXn 则A±B=[a±b 设A=[akln,B=[b H×P 则AB=∑ab AB≠BA k=12.矩阵的加减运算 设 则 设 则 , ij ij m n m n A a B b   = =         ij ij m n A B a b   =        , ik kj m n n p A a B b   = =     1 , n ik kj k m p AB a b AB BA =    =      