[tex]\bf \textit{middle point of 2 points }\\ \quad \\
\begin{array}{lllll}
&x_1&y_1&x_2&y_2\\
% (a,b)
A&({{ -8}}\quad ,&{{ 3}})\quad
% (c,d)
B&({{ x}}\quad ,&{{ y}})
\end{array}\qquad
% coordinates of midpoint
\left(\cfrac{{{ x_2}} + {{ x_1}}}{2}\quad ,\quad \cfrac{{{ y_2}} + {{ y_1}}}{2} \right)
\\\\\\
\left( \cfrac{x-8}{2}~,~\cfrac{y+3}{2} \right)=\stackrel{M}{(-2,1)}\implies
\begin{cases}
\cfrac{x-8}{2}=-2\\\\
x-8=-4\\
x=4\\
------\\
\cfrac{y+3}{2}=1\\\\
y+3=2\\
y=-1
\end{cases}[/tex]
