Question 936213
the midpoint of cm is (5 -11). TY for clarifying
Midpoint Pt(x,y):  ( {{{(x[1] + x[2])/2}}}, {{{(y[1] + y[2])/2  )}}})
(3, 5)
(x,  y)
(3-x)/2 = 5,  x = -7
......
(5 - y)/2 = -11,  x = 27
....
checking
(3, 5)
(-7,27) M = (5, -11)