Let equations of two lines are a1x + b1y + c1 = 0 and a2x + b2y + c2 = 0.
(i) Lines are consistent (unique solution) i.e. they meet at one point condition is
(ii) Lines are inconsistent (no solution) i.e. they do not meet at one point condition is
(iii) Lines are coincident (infinite solution) i.e. overlapping lines (or they are on one another) condition is