1-2r3,r2-3r3,r4-r3
-7 7 -12 0
-13 -3 -17 0
7 -2 7 3
-2 -1 -4 1
r3-3r4
-7 7 -12 0
-13 -3 -17 0
13 1 19 0
-2 -1 -4 1
按第4列展开
-7 7 -12
-13 -3 -17
13 1 19
r2+r3
-7 7 -12
0 -2 2
13 1 19
c3+c2
-7 7 -5
0 -2 0
13 1 20
按第2行展开 = -2*
-7 -5
13 20
=-2*(-7*20+5*13)
= 150