How to find value of $\lambda$ for following determinant by applying suitable row and column operation?
$\begin{pmatrix} \lambda-4 & 0 & 0 & -1 & -1 & -1 & -1\\ 0 & \lambda-5 & 0 & 0 & -1 & -1 & -1 \\ 1 & 1 & \lambda-4 & 1 & 1 & 0 & 0 \\ 0 & 1 & 1 & \lambda-4 & 1 & 1 & 0\\ 0 & 0 & 1 & 1 & \lambda-4 & 1 & 1\\ 0 & 0 & 0 & 1 & 1 & \lambda-3 & 1\\ 0 & 0 & 0 & 0 & 1 & 1 & \lambda-2 \end{pmatrix}=0$