1) Two parallel straight lines
2) Two perpendicular straight lines
3) Two lines passing through the origin
4) None of these
Solution:
Given f(x,y) = 0
∆ = 0
=> It represents a pair of straight lines.
Also given a + b = 0
=> Given lines are perpendicular.
So the equation represents two perpendicular straight lines.
Hence option (2) is the answer.
