7th British Mathematical Olympiad 1971 Problems

7th British Mathematical Olympiad 1971 Problems 1.  Factorise (a + b)7 - a7 - b7. Show that 2n3 + 2n2 + 2n + 1 is never a multiple of 3. 2.  Let a = 99 , b = 9a, c = 9b. Show that the last two digits of b and c are equal. What are they?