In: Advanced Math
Number Theory:
Let p be an odd number. Recall that a primitive root, mod p, is an integer g such that gp-1 = 1 mod p, and no smaller power of g is congruent to 1 mod p. Some results in this chapter can be proved via the existence of a primitive root(Theorem 6.26)
(c) Given a primitive root g, and an integer a such that a is not congruent to 0 mod p, prove that a is a square modulo p if and only if a = ge for an even number e. Use this to prove Euler's criterion: a is a square mod p if and only if a(p-1)/2 = 1 mod p.