Question
If n is a natural number, then 92n − 42n is always divisible by
(a) 5
(b) 13
(c) both 5 and 13
(d) None of these
[Hint : 92n − 42n is of the form a2n − b2n which is divisible by both a − b and a + b. So, 92n − 42n is divisible by both 9 − 4 = 5 and 9 + 4 = 13.]