1. The problem statement, all variables and given/known data Prove that for all natural numbers n, [tex]6^n -1[/tex] is divisible by 5. 2. Relevant equations 3. The attempt at a solution I'm not sure how to go about proving this. I know that 6 to the power of any natural number ends in 6, therefor subtracting 1 will always make it end in a 5. This proves that it is divisible by 5. I asked my maths tutor and his reply was "I'm not sure how to go about that", then after a while he said try induction. If I try to prove it by induction I can't get past the base case without being lost. Does anyone have any tips or advice?