0 1 1
1 2 1
1 1 0
1 0 0
0 1 0
0 0 1
Column 1, plus column 3.
1 1 1
2 2 1
1 1 0
1 0 0
0 1 0
1 0 1
1 line, plus 3 lines.
2 2 1
2 2 1
1 1 0
1 0 0
0 1 0
1 0 1
Subtract the third column from the second column.
2 1 1
2 1 1
1 1 0
1 0 0
0 1 0
1 - 1 1
The second line, subtract the third line.
2 1 1
1 0 1
1 1 0
1 0 0
0 1 0
1 - 1 1
Get the matrix C.
1 0 0
0 1 0
1 - 1 1