Given that M(1,-6) is the midpoint of AB and A(-2,-1) is one endpoint, what is the sum of the coordinates of point B?
- 2 + x
_______ = 1 multiply through by 2
2
-2 + x = 2
x + 2 + 2
x = 4
-1 + y
_____ = - 6 multiply through by 2
-1 + y = -12
y = -12 + 1
y = -11
B = ( 4 , - 11) sum of the coordinates = -7
