Question

Point A(-10,10) is the midpoint of segment BD. If the coordinate of B are (2, -4), then what are the coordinates of D?

Answer 1

Since A is the midpoint,

A = (B+D)/2
D = 2A-B
So, for the x-coordinate, that is 2(-10)-2 = -22
Check: -10 is halfway from -22 to 2 (12 from each end)
Now do y