思考题:能否以r<替上述两次行变换? 000 12 13 14 34 n2> r+r2 3 14 000 =(-1) 34 2 23 24 000 11 12 13 14 34 anx a,+>3 22 23 24 42 43 42 答:不能.2 3 1 2 34 2 34 41 42 43 44 41 42 43 44 11 12 1 21 22 23 3 14 24 11 12 13 14 21 22 23 24 0 0 0 ( 1) 0 0 0 r r r r a a a a a a a a a a a a a a a a a a a a a a a a a a   = − 思考题：能否以 代替上述两次行变换？ 1 3 34 34 41 11 12 1 42 3 14 11 1 43 44 41 4 21 22 23 24 21 22 23 2 2 13 2 3 4 1 4 4 4 4 0 0 0 ( 1) 0 0 0 r r a a a a a a a a a a a a a a a a a a a a a a a a a a  = − 答：不能. 1 3 r r 