Which of the following numbers is a divisor of (4915 - 1)?

Question: Which of the following numbers is a divisor of (4915 - 1)?Solution:an - bn is divisible by (a + b) when n is an even positive integer. Here, a & b should be prime number.(4915 - 1) ⇒ {(72)15 - 1)⇒ (730 - 1)Here, 30 is a positive integer. According to the concept, (730 - 1) is divisible by (7 + 1) i.e., 8. ∴ 8 is a divisor of (4915 - 1).