Question

Question 15
i. If n is a positive integer , then 7^2n – 4 is divisible by
(a) 25
(b) 26
(c) 2309
(d) none​

Answer 1

Expression is a

n

+b

n

The expression is never divisible by (a−b).

When n is odd, it is divisible by(a+b).

When n is even it is not divisible by (a+b)

So, it is not divisible by (a−b)(a+b)=a

2

−b

2

, when n is even.

The correct answer is option D.

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Answer 2

oops sorry................none is Answer