[tex]\begin{gathered} \text{mid point = (}\frac{x_1+x_2}{2},\frac{y_1+y_2}{2}\text{)} \\ (4,2)=(\frac{9+x_2}{2},\frac{5+y_2}{2}) \\ 4=\frac{9+x_2}{2} \\ 8=9+x_2 \\ x_2=8-9 \\ x_2=-1 \\ \\ 2=\frac{5+y_2}{2} \\ 4=5+y_2 \\ y_2=4-5 \\ y_2=-1 \end{gathered}[/tex]
it
