Решите уравнение x^2+y^2+4x-8y+20=0.

\[x^{2} + y^{2} + 4x - 8y + 20 = 0\]

\[\left( x^{2} + 4x + 4 \right) + \left( y^{2} - 8y + 16 \right) = 0\]

\[(x + 2)^{2} + (y + 4)^{2} = 0\]

\[\left\{ \begin{matrix} x + 2 = 0 \\ y + 4 = 0 \\ \end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix} x = - 2 \\ y = - 4 \\ \end{matrix} \right.\ \]

\[Ответ:( - 2; - 4).\]