Question

The midpoint of AB is M(1, 3). If the coordinates of A are (4, 1) what are the coordinates of B?

Answer 1

Midpoint formula: ((x1+x2)/2), (y1+y2)/2)
Plug in what you already know
((4+x2)/2), (1+y2)/2) = M(1/3)
(4+x2)/2 = 1
4 + x2 = 2, x2 = -2
(1+y2)/2 = 3
1 + y2 = 6, y2 = 5
Therefore the B coordinate = (-2,5)