If u=a1x+b1y+c1,v=a2x+b2y+c2=0 and a1a2=b1b2≠c1c2 then u+kv=0
a family of concurrent lines
a family of parallel lines
u = 0 or v = 0
none of these
u = 0, v = 0 are parallel lines but not identical . u+kv=0 represents a family of lines parallel to these lines.