There are infinite answers to this depending upon the length of the line
and the slope
We have midpoint = (4, 7)
The simplest possible points to look at would be a given distance
straight up and down or straight left and right from (4,7)
Perhaps the endpoints are n unit up and down: (4,7-n), (4,7+n)
Perhaps the endpoints are n units right and left: (4-n, 7), (4+n, 7)
Pick any number for n
Example: n=1 ... A = (4,6), B= (4,8) vertical line segment
A = (3,7), B = (5,7) horizontal line segment
If the line is not vertical or horizontal, we could pick a slope and then
use the point slope form to find the equation of the line... and then
look for points on the line equidistant from (4, 7)