得到同解方程组A3)x=b(3) b (1) au xIta1252ta13x3 a2x2+a2x3+…+a2=b2 a3x3+…+a3=b3 an2x3+…+amn=bn 若a3≠0,则此消去过程可依次进行下去A x b (3) (3) 得到同解方程组 = (1) (1) (1) (1) (1) 11 1 12 2 13 3 1 1 (2) (2) (2) (2) 22 2 23 3 2 2 (3) (3) (3) 33 3 3 3 ( 3 3 n n n n a x a x a x a b a x a x a b a x a b + + + + = + + + = + + = ) (3) (3) a x a b 3 nn n          + + =   若 a ( 3 3 3) ≠0， 则此消去过程可依次进行下去