A rectangle is graphed on the coordinate grid.
On a coordinate plane, side p has points (1, 4) and (3, 6), side q has points (3, 6) and (6, 3), side r has points (4, 1) and (6, 3), and side s has points (4, 1) and (1, 4).
Which represents the equation of a side that is perpendicular to side s?
y = negative x + 9
y = negative x + 5
y = x + 9
y = x + 3