What is the characteristic polynomial of the identity matrix I=(1001)I = \begin{pmatrix} 1 & 0 \\ 0 & 1 \end{pmatrix}I=(1001)?
λ2−1\lambda^2 - 1λ2−1
λ2−2λ+1\lambda^2 - 2\lambda + 1λ2−2λ+1
λ2+1\lambda^2 + 1λ2+1
λ2−2\lambda^2 - 2λ2−2