What is the characteristic polynomial of the matrix A=(01−10)A = \begin{pmatrix} 0 & 1 \\ -1 & 0 \end{pmatrix}A=(0−110)?
λ2+1\lambda^2 + 1λ2+1
λ2−1\lambda^2 - 1λ2−1
λ2+λ+1\lambda^2 + \lambda + 1λ2+λ+1
λ2−λ+1\lambda^2 - \lambda + 1λ2−λ+1