If two lines a1x+b1y+c1=0 and a2x+b2y+c2=0  cut the coordinate axes in concyclic points, then

Equation of a curve through the intersection of the lines and the coordinates axes is(a1x+b1y+c1)(a2x+b2y+c2)+λxy=0  If it represents a circle, co-eff of x2  and y2  are equal ⇒ a1a2=b1b2.