【a1,a2,a3,a4,a5,a6,a7,a8,为{1,2,3,4,5,6,7,8,9,10,11,12,13,14,1516,17}中八个不同的数,求证在a1--a8中至少有三对（i,j),使得ai-aj的差相等（ai-aj=K,K>0)求详解,】

　　a1,a2,a3,a4,a5,a6,a7,a8,为{1,2,3,4,5,6,7,8,9,10,11,12,13,14,1516,17}中八个不同的数,求证在a1--a8中至少有三对（i,j),使得ai-aj的差相等（ai-aj=K,K>0)求详解,