Question 121003
Lines that are perpendicular have slopes that are NEGATIVE RECIPROCALS of one another.  The slope of a line in slope-intercept form is always the coefficient of x.  Therefore the slopes of the given lines are 


a) 4/7
b) 3
c) -1/3
d) 1/3


Of these numbers the slopes 3 and -1/3 are negative reciprocals, so the answer is b and c.


R^2