What is the characteristic polynomial of a 2×22 \times 22×2 identity matrix?
(λ−1)2(\lambda - 1)^2(λ−1)2
λ2−1\lambda^2 - 1λ2−1
λ2+1\lambda^2 + 1λ2+1
λ2−2λ\lambda^2 - 2\lambdaλ2−2λ