r2+r1、r3-r1*2、r4-r1|1 1 -1 3|0 0 1 40 3 4 -50 1 4 -1r3-r4*3|1 1 -1 3|0 0 1 40 0 -8 -20 1 4 -1r2+r3*2|1 1 -1 3|0 0 -15 00 0 -8 -20 1 4 -1r2、r4交换；c3、c4交换|1 1 3 -1|0 1 -1 40 0 -2 -80 0 0 -15=1*1...