Question Detail
Question
n² - 1 is divisible by 8, if n is:
Correct Answer
Option C is the correct answer.
Detailed Explanation
If n is odd, let n = 2k+1, then n² - 1 = (2k+1)² - 1 = 4k² + 4k = 4k(k+1). Since k(k+1) is always even, 4k(k+1) is divisible by 8. If n is even, n² - 1 is odd, so not divisible by 8.
Hint
Test with odd and even numbers to see the pattern.