Explanation:
M(-2,0)
A(-6,8)
M ia a mid point of AB
we know that
if mid point coordinates (x,y)
x=(x1+x2)/2
and
y=(y1+y2)/2
here
x=-2 , y=0
x1=-6 , y1=8
so coordinates of point B
-2=(-6+x2)/2
-4=-6+x2
x2=2
and
0=(8+y2)/2
0=8+y2
y2=-8
therefore coordinates of point B (2,-8)