41七1+412X2+.+a1n火m 21X1+22X2+.+42mXn =(x1,x2,xn) mK1+0n2x2+.+0nmXn 12 . 1 L21 L22 X2 =(1,x2.,xn) ·: 11 1 12 2 1 21 1 22 2 2 1 2 1 1 2 2 ( , , , ) n n n n n n n nn n a x a x a x a x a x a x x x x a x a x a x   + + +   + + +   =     + + +   11 12 1 1 21 22 2 2 1 2 1 2 ( , , , ) n n n n n nn n a a a x a a a x x x x a a a x          =         