\[\left\{ \begin{matrix} y = x - 2\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ x^{2} + y^{2} - 2x - 4y = - 1 \\ \end{matrix} \right.\ \]
\[2x^{2} - 6x + 13 = 0\]
\[D = ( - 6)^{2} - 4 \cdot 2 \cdot 13 =\]
\[= 36 - 104 = - 68 < 0 -\]
\[нет\ решения.\]
\[\Longrightarrow ч.т.д.\]