If $$ A = \begin{pmatrix} k + 1 & 2 \\4 & k - 1 \end{pmatrix}$$ is a singular matrix, then possible values of k are
If $ A = \begin{bmatrix} 2 & 2 \\3 & 4 \end{bmatrix}, \quad \text{then} \quad A^{-1} \text{ equals to} $