好像刚做过这个题目
0 1 x 1
1 0 1 x
x 1 0 1
1 x 1 0
r3-xr2,r4-r2
0 1 x 1
1 0 1 x
0 1 -x 1-x^2
0 x 0 -x
r3-r1,r4-xr1
0 1 x 1
1 0 1 x
0 0 -2x -x^2
0 0 -x^2 -2x
r4-(1/2)xr3
0 1 x 1
1 0 1 x
0 0 -2x -x^2
0 0 0 -2x+(1/2)x^3
行列式 = 2x(-2x+x^3/2) = x^4 -4x^2.
= x^2 (x-2)(x+2).
解为 x = 0 or 2 or -2