相似矩阵的特征值相同, 故行列式相同,迹相同
|A| = -2(x-2) = |B| = -2y
tr(A) = -2-x+1 = tr(B) = -1+2+y
所以有
x - y = 2
x + y = -2
故有 x = 0, y = -2