1 2 2 2
2 2 2 2 r2-r1*2
2 2 3 2 r3-r1*2
2 2 2 4 r4*r1*2
=
1 2 2 2
0 -2 -2 -2
0 -2 -1 -2
0 -2 -2 0
=
-2 -2 -2
-2 -1 -2 r2-r1
-2 -2 0 r3-r1
=
-2 -2 -2
0 1 0
0 0 2
=-2x1x2
=-4
1 2 2 2
2 2 2 2 r2-r1*2
2 2 3 2 r3-r1*2
2 2 2 4 r4*r1*2
=
1 2 2 2
0 -2 -2 -2
0 -2 -1 -2
0 -2 -2 0
=
-2 -2 -2
-2 -1 -2 r2-r1
-2 -2 0 r3-r1
=
-2 -2 -2
0 1 0
0 0 2
=-2x1x2
=-4