For all nϵN, 3×52n+1+23n+1 is divisible by
19
17
23
25
(b) and (c)
Given that, 3×52n+1+23n+1
For n = 1
=3×52(1)+1+23(1)+1
=3×53+24
=3×125+16=375+16=391
Now, 391 = 17 × 23
which is divisible by both 17 and 23.
If n ∈ N, then 72n + 23n−3.3n−1 is always divisible by