The set of all values of

The set of all values of $\lambda$ for which the system of linear equations:

$2 x_{1}-2 x_{2}+x_{3}=\lambda x_{1}$

$2 x_{1}-3 x_{2}+2 x_{3}=\lambda x_{2}$

$-\mathrm{x}_{1}+2 \mathrm{x}_{2}=\lambda \mathrm{x}_{3}$

has a non-trivial solution