自例4.A=B=(1,2,3)-(1)-23-(11),023BA=(1,2,3)=(1×1+2×2+3×3)=(14) =144.2矩阵的运算V§4.2 矩阵的运算 例4． ( ) 1 2 , 1,2,3 3 A B   = =       ( ) 1 1 2 3 2 1,2,3 2 4 6 , 3 3 6 9 AB     = =             ( ) 1 1,2,3 2 3 BA   =       =  +  +  (1 1 2 2 3 3)= = (14) 14