Question

The equation axy+bx+cy+d=0 represents a pair of straight lines, then

(a) bc=ad

(b) the lines are parallel

(c) the lines cannot be parallel

(d) the lines are coincident

Answer 1

the lines cannot be parallel because the coefficients of x² and y²     are 0 but the coefficients x and y are not 0.hence the lines are in the form "l₁x+m₁=0"and "l₂y+m₂=0" which are clearly perpendicular. so the aanswer is (c)