



 
Hi Ethan, You haven't said if $a$ is positive or negative so I am going to assume that $a$ is positive. Again I don't know if $S$ is above or below the Xaxis so I am going to assume it is above the Xaxis. I added one point $A$ so that $SA$ is perpendicular to the Xaxis. What is the distance from $R$ to $A?$ What is the distance from $S$ to $A?$ Maybe Pythagoras can help. What are the coordinates of $S?$ Suppose that $S$ is below the Xaxis. What are the coordinates of $S?$ Hence you have two possible answers for the question you were asked. Now suppose $a$ is negative. Does that give you two more possible answers? Penny 



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