# show this a primitive root question [closed]

if $$n$$ be positive integers,and such

(1):$$\prod_{1\le i\le n,(i,n)=1}i\equiv -1\pmod n$$ (2):there exsit $$a,$$ such $$a$$ is a primitive root modulo $$n$$.

show that $$(1)\Longleftrightarrow (2)$$

his problem comes from the fact that when I deal with other problem,and I can't prove it,Thanks

## closed as off-topic by Carl Mummert, Alexander Gruber♦Feb 25 at 7:19

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• Related 1,2. A cyclic group of an even order has a single element of order two. – Jyrki Lahtonen Feb 9 at 14:14
• Hello,have a simple methods to prove it? – inequality Feb 9 at 14:17