Question 775314
(8+x)/2 = -10


8+x = 2*(-10)


8+x = -20


x = -20 - 8


x = -28


-------------------------------------------------------


(9+y)/2 = 4


9+y = 2*4


9+y = 8


y = 8 - 9


y = -1


-------------------------------------------------------


So the other endpoint is <font color="red">(-28, -1)</font>