I have a question; Let m have a prime factor p \equiv 1 (mod 4). Then Euler function \varphi(m) is divisible by 4. Let x = r^{\varphi(m)}, then m|(x^4-1) and x^4-1=(x^2-1)(x^2+1). As gcd(x^2-1,x^2+1)|2, either x^2-1 or x^2+1 is divisible by m. My book says here because of the nature of a...