Question 97519
I am assuming that you meant R (4,3) and S (5,1)

Slope of a line passing through points (x1,y1) and (x2,y2) is given by 
 Slope = {{{(y2-y1)/(x2-x1)}}}

using the formula above slope = {{{(1-3)/(5-4)}}}
slope = {{{-2/1}}} 
      =-2

we use the following fact that the product of the slope of a line and the slope of the line perpendicular to it is -1

so if M is the slope of any perpendicular
M* -2 = -1 
M= 1/2