Answer:
[tex]=\left(\frac{21}{2},\:-4\right)[/tex]
Step-by-step explanation:
[tex]\mathrm{Midpoint\:of\:}\left(x_1,\:y_1\right),\:\left(x_2,\:y_2\right):\quad \left(\frac{x_2+x_1}{2},\:\:\frac{y_2+y_1}{2}\right)\\\\\left(x_1,\:y_1\right)=\left(18,\:-17\right),\:\left(x_2,\:y_2\right)=\left(3,\:9\right)\\\\=\left(\frac{3+18}{2},\:\frac{9-17}{2}\right)\\\\Refine\\=\left(\frac{21}{2},\:-4\right)[/tex]
