\[\left( x^{2} + y^{2} + 6y \right)(x - y) = 0\]
\[x^{2} + y^{2} + 6y + 9 - 9 = 0\]
\[x^{2} + (y + 3)^{2} = 3^{2}\]
\[Точка\ O(0; - 3);\ \ \ R = 3.\]
\[x - y = 0\]
\[y = x\]