1-xr2
0 1-x^2 -x 0
1 x 1 0
0 1 x 1
0 0 1 x
r1-(1-x^2)r3
0 0 x^3-2x x^2-1
1 x 1 0
0 1 x 1
0 0 1 x
r1-(x^3-2x)r4
0 0 0 -x^4+3x^2-1
1 x 1 0
0 1 x 1
0 0 1 x
= (-1)^(1+4)(-x^4+3x^2-1)
= x^4-3x^2+1
1-xr2
0 1-x^2 -x 0
1 x 1 0
0 1 x 1
0 0 1 x
r1-(1-x^2)r3
0 0 x^3-2x x^2-1
1 x 1 0
0 1 x 1
0 0 1 x
r1-(x^3-2x)r4
0 0 0 -x^4+3x^2-1
1 x 1 0
0 1 x 1
0 0 1 x
= (-1)^(1+4)(-x^4+3x^2-1)
= x^4-3x^2+1