Question

The midpoint of AB is M (-1, -5). If the coordinates of A are (3, -8), what are the coordinates of B?

Answer 1

coordinates of point B are (-5, -2)

Explanation:

Recall that the midpoint of the segment that joins (x1, y1) with (x2, y2) is given by:

( (x1 + x2)/2 , (y1+y2)/2)

Therefore, given the information about the midpoint being (-1, -5) and A being (3, -8) we get:

For the x value (x2) of point B:

-1 = (3 + x2) / 2 then -2 = 3 + x2 and finally solving for x2; x2 = -2 - 3 = -5

For the y value (y2) of point B:

- 5 = (-8 + y2) / 2 then -10 = - 8 + y2 and finally y2 = -10 + 8 = - 2

Then point B has the coordinates: (-5, -2)