The slope of the line that passes through (-9,4) and (1,2) is -1/5 so in order to find the slope that is perpendicular to it, you need to find out with of these pairs of points has a slope that is the negative reciprocal of -1/5 which is 5. So the only points that have the slope of 5 are (2,15) and (4,25).
What you need to do is find the slope of both lines. Perpendicular lines are the negative inverse of each other. The slope of the lie between points R and F is (2-4)/(1+9)=-1/5. Now you need to find the line where the slop is 5. If you look at D, the slope of the line those points lie on is (25-15)/(4-2)=5 which makes D the answer.
