化为行最简矩阵
看有几行不全为零
有几行不全为零,矩阵的秩就是几
(1)秩:2
1 0 1/2 1/4
0 1 -3/2 5/4
0 0 0 0
(2)秩:3
1 0 3 2 0
0 1 2 -1 0
0 0 0 0 1
0 0 0 0 0
(3)秩: 3
1 0 3 2 0
0 1 2 -1 0
0 0 0 0 1
0 0 0 0 0