5 1 1 1
-2 2 -1 4
-2 -3 -1 -5 --------（-1）*r3+r4
0 1 2 11
5 1 1 0
-2 2 -1 5 --------（-1）*r3+r2;(-5)r3+r1
-2 -3 -1 -4
0 1 2 9
0 0 1 0
3 3 -1 5 ---------4*4变为3*3
3 -2 -1 -4
-10 -1 2 9
3 3 5
3 -2 -4 -----9r2+r3;-10r2+r1
-10 -1 9
-27 3 32
23 -2 -22 ------3*3变为2*2
0 -1 0
-27 32
23 -22
=22*27-23*32=-142