Explanation:
Here,we have,
(x, y) =M(0,-6)
(x1, y1) =A(9,-3)
(x2, y2) =coordinates of B=?
Using midpoint formula, we get,
x=x1+x2÷2
or, 0=9+x2÷2
or, 0×2=9+x2
or, 0-9=x2
or, x2=-9
therefore, x2=-9
Now,
y=y1+y2÷2
or, -6=-3+y2÷2
or, -6×2=-3+y2
or, -12+3=y2
or, y2=-9
therefore, y2=-9
Hence, the coordinates of B are (-9, -9)..