The Chief Examiner reported that this question was one of the most popular questions as it was attempted by majority of the candidates.  The report further stated that while they were able to apply the principles of combination correctly, majority of them were not able to expand and simplify the resulting equation because it involved letters not just numbers

Candidates were reported to have shown that  p + 1 C4    =     =    =  [(p+1)(p)(p-1)(p-2)].  Similarly  p − 1 C4  =  = (p-1)(p-2)(p-3)(p-4)].  Therefore, p + 1 C4 -  p – 1C4   =  -  =     =  [ p2 + p – p2 + 7p – 12] =   [8p – 12] =