Two Points on a Line , can we reach the midpoint?
Source: 2021 Iran second round mathematical Olympiad P1
May 15, 2021
combinatoricsgeometry
Problem Statement
There are two distinct Points and on a line. We color a point on segment , distinct from and midpoint of segment to red. In each move , we can reflect one of the red point wrt or and color the midpoint of the resulting point and the point we reflected from ( which is one of or ) to red. For example , if we choose and the reflection of wrt to is , then midpoint of would be red. Is it possible to make the midpoint of red after a finite number of moves?