Hint for Section G.1 Question 2

2. Check the group axioms:

• closure under addition modulo 7: if you add any pair of elements in Z₇, is the result also an element of Z₇?
• associativity: does (a + b) + c = a + (b + c) for a, b, c Z₇?
• identity: do we have e Z₇ such that e + a = a = a + e for all a Z₇?
• inverse: for all a Z₇, do we have an a^-1 such that a + a^-1 = e = a^-1 + a?

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