What is the characteristic polynomial of the matrix A=(2112)A = \begin{pmatrix} 2 & 1 \\ 1 & 2 \end{pmatrix}A=(2112)?
λ2−4λ+3\lambda^2 - 4\lambda + 3λ2−4λ+3
λ2+4λ+3\lambda^2 + 4\lambda + 3λ2+4λ+3
λ2−3λ+4\lambda^2 - 3\lambda + 4λ2−3λ+4
λ2−4λ−3\lambda^2 - 4\lambda - 3λ2−4λ−3