22(1264). Represent the expression $2 x^{2}+2 y^{2}$ as a sum of two squares.
Solution.

$$
\begin{aligned}
2 x^{2}+2 y^{2}= & \left(x^{2}+2 x y+y^{2}\right)+\left(x^{2}-2 x y+y^{2}\right)= \\
& =(x+y)^{2}+(x-y)^{2}
\end{aligned}
$$