Question: 7^n-1 is divisible by 6?
Answer: Inductive step : Assuming the statement is true for case n , i.e. 7 n -1 is divisible by 6 then for case n+1 : 7 n+1 - 1 = 7 * 7 n - 1 = 7 * (7 n -1 ) + 6 is also divisible by 6 since both terms are divisible by 6.