Question

What are the coordinates of B?

Answer 1

We can do 'point' arithmetic.

M = (A+B)/2

2M = A+B

B = 2M - A

We have M(3, -4) and A(8, -5)

B = 2(3, -4) - (8, -5) = (6,-8) - (8,-5) = (-2, -3)

Check:

(A+B)/2 = ( (8+-2)/2, (-5+ -3)/2) = (3, -4) good

Answer: (-2, -3)