The midpoint of segment XY is (6, -3). The coordinates of one endpoint are X(-1, 8). Find the coordinates of endpoint Y.

Answer 1

(6,-3) is halfway from (-1,8) to Y
6-(-1) = 7
so, add 7 to 6 and get 13.
So, the x-coordinate of Y is 13
-1..........6..........13
6 is halfway from -1 to 13
(x+(-1))/2 = 6
x-1 = 12
x = 13

now do the same for y.