If the lines x=az+b, y=cz+d; x=a1z+b1, y=c1z+d1 are perpendicular then
aa1+cc1+1=0
aa1+cc1−1=0
aa1+bb1+1=0
aa1+dd1−1=0
x−ba=y−dc=z1, x−b1a1=y−d1c1=z1 both are perpendicular