a=
3 1 0 1
1 -1 2 -1
1 3 -4 4 r1-3r2,r3-r2
~
0 4 -6 4
1 -1 2 -1
0 4 -6 5 r3-r1,交换r1和r2
~
1 -1 2 -1
0 4 -6 4
0 0 0 1 r1+r3,r4-4r3
~
1 -1 2 0
0 4 -6 0
0 0 0 1 r1+0.25r2,r2 /2
~
1 0 1/2 0
0 2 -3 0
0 0 0 1
这样就散逗已经化老哪为了冲含卖最简
显然矩阵的秩为R(A)=3