For what value(s) of kkk is the matrix (k22k)\begin{pmatrix} k & 2 \\ 2 & k \end{pmatrix}(k22k) singular (non-invertible)?
k=2k = 2k=2 only
k=−2k = -2k=−2 only
k=2k = 2k=2 or k=−2k = -2k=−2
No solution