西安毛子科技大学三XIDIANUNIVERSITY解A可以看成是由3阶单位矩阵E经4次初等变换，r2r3, C +2c3, (-1)r3,(-1)c.. A= PPEPP= PPP,P0000P =01P0021100001001P4 =001P, =0000-1 = A P P EP P 3 1 2 4 . = P3P1P2P4 , 0 1 0 0 0 1 1 0 0 1           P = , 2 0 1 0 1 0 1 0 0 2           P = , 0 0 1 0 1 0 1 0 0 3           − P = . 0 0 1 0 1 0 1 0 0 4           − P = 解 A 可以看成是由3阶单位矩阵 E 经4次初等变换, ( ) ( ) 2 3 1 3 3 1 3 r  r , c + 2c , − 1 r , − c