Question 1091607
midpoint between (x1, y1) and (x2, y2) is the average of the x s and the average of the y s
Here, one has the midpoint, so work backward to get the other point.
the midpoint for the x values is -2.  One value is -8, so (-8 +x2)/2=-2, the average of the two points is -2
-2=(-8 +x2)/2
multiply by 2 and -4=x^2-8, and x2=4.
Do the same thing with y
You can think of it this way.  The middle is y=1, and one side is 3.  That is two away from the middle, so the other side has to be 2 on the other side of the middle, or -1
The coordinates of B are (4, -1).
Check by adding the A and B points and taking the average: -8+4 divided by 2 is -4/2=-2.
-1+3/2 is 2/2=1