I'll do the first one to get you started.
Find the slope of the line between R (6,-2) and S (-1,8) to get
m = (y2-y1)/(x2-x1)
m = (8-(-2))/(-1-6)
m = (8+2)/(-1-6)
m = 10/(-7)
m = -10/7
The slope of line RS is -10/7
Next, we find the slope of line DF
m = (y2 - y1)/(x2 - x1)
m = (4-11)/(11-(-1))
m = (4-11)/(11+1)
m = -7/12
From here, we multiply the two slope values
(slope of RS)*(slope of DF) = (-10/7)*(-7/12)
(slope of RS)*(slope of DF) = (-10*(-7))/(7*12)
(slope of RS)*(slope of DF) = 10/12
(slope of RS)*(slope of DF) = 5/6
Because the result is not -1, this means we do not have perpendicular lines here. Any pair of perpendicular lines always has their slopes multiply to -1. This is assuming neither line is vertical.
I'll let you do the two other ones. Let me know what you get so I can check your work.
