Suppose the coordinate of A is 0
AR = 20
Let M be the midpoint of line AR
Since A is given to be zero, R can be located to the left or right of A
If R is located to the left of A, then R = -20 and the midpoint m will be:
[tex]M\text{ = }\frac{0+(-20)}{2}=\text{ }\frac{0-20}{2}\text{ = }\frac{-20}{2}\text{ =-10}[/tex]
Similarly,
If R is located to the right of A, then R = 20 and the midpoint M will be:
[tex]M\text{ =}\frac{0+20}{2}\text{ = }\frac{0+20}{2}\text{ = }\frac{20}{2}\text{ = 10}[/tex]
Therefore, the possible coordinates of the midpoint of AR are -10 or 10
