if n∈N, then 72n+33n−3⋅3n−1  is always divisible by

putting,  n=1 is 72n+23n−3⋅3n−1, we get 72.1+23.1−3⋅31−1=7220⋅30=49+1=50      (1)Also, for n = 272.2+23.2−3⋅32−1=2401+24=2425     (2)From Eq. (1) and (2), it is always divisible by 25.