Question

21. 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: 921 – 42n is of the form a2n – b2n which is divisible by both a b and a + b. So, 921 – 421 is divisible by both 9-4 = 5 and 9 + 4 = 13.] те​

Answer 1

Answer:

(c) Both 5 and 13

Step-by-step explanation:

81  n  −16  n  ⇒a  n  −b  n

is always divisible by (a−b)

(81−16)=65

∴ So factors are both 5 and 13