قسم الإعلام الآلي

you should insert a big parenthesis hanen

\begin{equation}
     (\bar{x},\bar{y}) =  \bigg(

                                         \frac{1}{N} \sum_{P_{(x,y)} \in R} X , \frac{1}{N} \sum_{P_{(x,y)} in R} Y

                                    \bigg)
 \end{equation}

\begin{equation}
(\bar{x},\bar{y}) = \bigg (
\frac{1}{N} \sum_{P_{(x,y) \in R}} X,\frac{1}{N} \sum_{P_{(x,y) \in R}} y
\bigg )
\end{equation}