A=0 2 13 3 21 0 1 r2-3r3，交换r1和r3～1 0 10 3 -10 2 1 r2-r3～1 0 10 1 -20 2 1 r3-2r2，r3 /5～1 0 10 1 -20 0 1 r1-r3，r2+2r3～1 0 00 1 00 0 1这样就完成了初等行变换
