Answer:
B (2, 4)
Step-by-step explanation:
A (-1,-9); M (0.5, -2.5); B (xB, yB)
M is the midpoint of AB, therefore we have these 2 equations:
(*) xA + xB = 2. xM
(**) yA + yB = 2. yM
(*) <=> xB = 2. xM - xA = 2x0.5 - (-1) = 1 + 1 = 2
(**) <=> yB = 2. yM - yA = 2x(-2.5) - (-9) = -5 + 9 = 4
So, B (2, 4)
