Use the mathematical induction to prove that 7^n -1 is divisible by 6 whenever n is a positive integer

Step-by-step explanation:

1) first of all, let s check for n = 1

that s true

2) We assume that this is true for n

is divisible by 6

what about ?

we know that there is a k natural so that

so

then

so

so it means that is divisible by 6

3) finally as this is true for n=1 and if this is true for n then it is true for n+1 we can conclude that is divisible by 6 for n positive integer

your answer is the frist one

hop i