## anonymous 3 years ago prove 7 divides 2n-1 = 3divides n

1. anonymous

Prove tht $\forall n \in \mathbb{N} , 7|(2^n-1) <=> 3|n$

2. anonymous

a hint is to look at the multiplication table (for $\mathbb{Z}/7\mathbb{Z}$ and computer powers of 2 mod 7, and to notice how they repeat

3. anonymous

|dw:1352059720286:dw|

4. anonymous

thats not a proof

5. anonymous

oh yaa u are right!

6. anonymous

1. it is not a proof 2. 3 divides n means n/3 not 3/n :p

7. anonymous

sorry :P