If the system of equations
 $\begin{array}{l}2\mathrm{x}+\mathrm{y}-\mathrm{z}=5\\ 2\mathrm{x}-5\mathrm{y}+\mathrm{\lambda z}=\mathrm{\mu }\\ \mathrm{x}+2\mathrm{y}-5\mathrm{z}=7\end{array}$
has infinitely may solutions, then $(\mathrm{\lambda }+\mathrm{\mu }{)}^2+(\mathrm{\lambda }-\mathrm{\mu }{)}^2$ is equal to