Question: 8^n-1 is divisible by 7?
Answer: Prove by induction that 8n−1 is divisible by 7 Prove by induction that 8n−1 for any positive integer n is divisible by 7. Hint: It is easy to represent divisibility by 7 in the following way: 8n−1=7⋅k where k is a positive integer.