利用矩阵的乘法,(83)式可写成利用矩阵的乘法，（8.3）式可写成                     =    = = = n j n j j n j j j n j j j n n a x a x a x f x x x x x x 1 1 2 1 1 1 2 1 2 ( , , , ) ( , , , )                                = n n n n n n n n x x x a a a a a a a a a x x x         2 1 1 2 2 1 2 2 2 1 1 1 2 1 1 2 ( , , , )