\[1)\ A( - 1;\ - 6),\ \ \ B(5;\ - 6):\]
\[C_{x} = \frac{- 1 + 5}{2} = 2;\ \ \]
\[C_{y} = \frac{- 6 - 6}{2} = - 6.\]
\[Ответ:\ \ C(2;\ - 6).\]
\[2)\ A(3;\ 1),\ \ \ B(3;\ 5):\]
\[C_{x} = \frac{3 + 3}{2} = 3;\ \ \]
\[C_{y} = \frac{1 + 5}{2} = 3.\]
\[Ответ:\ \ C(3;\ 3).\]
\[3)\ A(3;\ - 5),\ \ \ B( - 1;\ 3):\]
\[C_{x} = \frac{3 - 1}{2} = 1;\ \ \ \]
\[C_{y} = \frac{- 5 + 3}{2} = - 1.\]
\[Ответ:\ \ C(1;\ - 1).\]