If the planes  bx−ay=n, cy−bz=l, az−cx=m intersects in a line then the value of  al+bm+cn is

b−a0n0c−bl−c0am R3→bR3+c R1  ~  b−a0n0c−bl0−acabbm+cn R3→R3+aR2 ~b−a0n0c−bl000al+bm+cn   Three planes intersects in a line⇒     System of equations have  infinitely  many solutions     ⇒  a l+bm+cn=0