Answer:
(5, 21)
Explanation:
The x-coordinate of the midpoint of a segment is half of the sum of the x-coordinates of the endpoints.
The y-coordinate of the midpoint of a segment is half of the sum of the y-coordinates of the endpoints.
Let the unknown point have coordinates (x, y).
x-coordinate:
(5 + x)/2 = 5
5 + x = 10
x = 5
y-coordinate:
(-1 + y)/2 = 10
-1 + y = 20
y = 21
The other endpoint has coordinates (5, 21).