Question

if [x] denotes greatest integer < or = x ,
then prove that
C(n,3) - [ n/3 ]
is a natural no. , divisible by 3 for all integer n> or =3

Answer 1

C(n,3) here denotes comination,
for e.g.
C(4,3) = 4! / (4-3)! (3)!
likewise..

Answer 2

n can have only 3 from ...
1) 3k
2) 3k+1
3) 3k+2