# Suppose that a has order 3 modulo...

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• Mar 28th 2010, 07:25 PM
NikoBellic
Suppose that a has order 3 modulo...
Suppose that a has order 3 modulo some p. Prove that a+1 has order 6 modulo p. [Hint: Take a^3 - 1 (which is 0 modulo p) and factor it to get a new expression for a+1.]
• Mar 28th 2010, 07:32 PM
Bruno J.
Well clearly $a \neq 1$. Since $0=a^3-1=(a-1)(a^2+a+1)$ we have $0=a^2+a+1$. I think you can take it from here!
• Mar 28th 2010, 07:40 PM
chiph588@
Quote:

Originally Posted by NikoBellic
Suppose that a has order 3 modulo some p. Prove that a+1 has order 6 modulo p. [Hint: Take a^3 - 1 (which is 0 modulo p) and factor it to get a new expression for a+1.]

See here.