你这个是行列式么?
|x 1 1| |x + 2 1 1| |1 1 1| |1 1 1|
|1 x 1| = |x + 2 x 1| = (x + 2)|1 x 1| = (x + 2)|0 x - 1 0|
|1 1 x| |x + 2 1 x| |1 1 x| |0 0 x - 1|
= (x + 2)|x - 1 0| = (x + 2)(x - 1)²
|0 x - 1|
所以(x + 2)(x - 1)² = 0
==> x = -2 或 x = 1(重根)