Trong mặt phẳng tọa độ Oxy cho hai điểm 

D

- Hướng dẫn giải

Gọi I(a;b)

\(M' = {V_{\left( {I; - \frac{1}{2}} \right)}}\left( M \right) \Leftrightarrow \overrightarrow {IM'} = - \frac{1}{2}\overrightarrow {IM} \)

\(\begin{array}{l} \Leftrightarrow \left\{ \begin{array}{l} - 3 - a = - \frac{1}{2}\left( {4 - a} \right)\\5 - b = - \frac{1}{2}\left( {6 - b} \right)\end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l} - 6 - 2a = - 4 + a\\10 - 2b = - 6 + b\end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l} - 2 = 3a\\16 = 3b\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}a = - \frac{2}{3}\\b = \frac{{16}}{3}\end{array} \right.\\ \Rightarrow I\left( { - \frac{2}{3};\frac{{16}}{3}} \right)\end{array}\)