Let a be a square matrix of order 2, a, β be linearly independent 2-dimensional sequence vectors, AA = 0, a β = a + β, then the nonzero eigenvalues of A

Let a be a square matrix of order 2, a, β be linearly independent 2-dimensional sequence vectors, AA = 0, a β = a + β, then the nonzero eigenvalues of A

It is known that a (α, β) = (a α, a β) = (0, α + β) = (α, β) K
K =
0 1
0 1
Since α and β are linearly independent, they are reversible
So a is similar to K
It is easy to know that the eigenvalues of K are 0,1
So the nonzero eigenvalue of a is 1