
#1
Nov404, 02:36 PM

P: 212

If a and N coprime, a < N and r is even how can
a^(r) = 1 mod(N) be written as a^(r)  1 = 0 mod(N) ? I don't know much number theory (I'm a physics student) Thanks 



#2
Nov404, 02:45 PM

Sci Advisor
HW Helper
P: 1,996

Hi, the conditions you list at the start don't matter for what you've just asked (a, N coprime, etc). For any a,b, and N,
a=b mod (N) if and only if N divides ab if and only if N divides (ab)0 if and only if ab=0 mod(N) Working mod N you can add, subtract and multiply as normal (division isn't always possible!), you just have the luxury of reducing things mod(N) afterwards. 



#3
Nov404, 03:54 PM

P: 212

ahh i see what you did there.. thanks!



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