Question 90453


    Determine which two equations represent perpendicular lines.
(a) y = 5/8 x – 3
(b) y = 3x – 5/8
(c) y = -1/3 x + 5/8 
(d) y = 1/3 x – 5/8 


   The condition  for the two lines to be perpendicular is 

          product of their slopes = -1

     From th above given eq'ns  (b) and (c)  their slopes are 3 and -1/3 

       hence their product = 3*-1/3 = -1 which satisfies the condition
   (b)  and   (c) are perpendicular to each other