calculate midpoint between A(1.-2) and C(5,9)

$$\left(\frac{1+5}{2},\frac{-2+9}{2}\right)\\\\
=\left(\frac{6}{2},\frac{7}{2}\right)\\\\
=(3,3.5)$$

.

$${\frac{\left(\begin{pmatrix}
{\mathtt{1}}
\\
-{\mathtt{2}}
\end{pmatrix}
{\mathtt{\,\small\textbf+\,}}\begin{pmatrix}
{\mathtt{5}}
\\
{\mathtt{9}}
\end{pmatrix}
\right)}{{\mathtt{2}}}} = \begin{pmatrix}
{\mathtt{3}}
\\
{\mathtt{3.5}}
\end{pmatrix}$$

.