i have 2 problem and need ur help

let r be a primitive root of the integer n . prove that r^k is a primitive root of n if and only if gcd(k,phi(n))=1

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for prime p>3 prove that the primitive root of p occur in pairs r,r' where rr' equivelent to 1(modp)

hint (take r' as r^(p-2) )

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plz any one can help me with them ?