λ is the eigenvalue and λ3 is wrong. For the matrix, there is ∑λ=∑aii (sum of eigenvalues = sum of diagonal elements of the matrix), and you make an error in the second step, so that a row of the matrix is titled as α=(x, y, z), with X+y+z = 3, α A 1 =-X+. Coefficient matrix b = [1 1 1], x = (x, y, z) t, b = (3 3,0,0) t, bx = b, r (b) = 3 = r (b | b), bx.

- 1 2 - 1

0 - 1 1

Therefore, the row vector of a can only be x = (1, 1, 1) t, and a = [1 1].

1 1 1

1 1 1

Obviously, λ1+λ 2+λ 3 = a1+a22+a33 = 3, and λ 1=λ2=0, then λ3=3.