Consider three planesP1:x−y+z=1,P2:x+y−z=−1and P3:x−3y+3z=2Let L1,L2,L3 be the lines of intersection of the planes P2 and P3,P3 and P1,P1 and P2 , respectively.
Statement I At least two of the lines L1,L2 and L3 are non-parallel.
Statement II The three planes do not have a common point.