Ax2+By2 = 1 ... (1) Ax + By dxdy = 0 ... (2) A + By dx2d2y + B(dxdy)2 = 0 ... (3) From (2) and (3) x {−Bydx2d2y−B(dxdy)2} + By dxdy = 0 Dividing both sides by –B, we get xy dx2d2y + x (dxdy)2 - y dxdy = 0 Which is a DE of order 2 and degree 1