Let Z be the integers.
(a) Let C1 = {(a, a) | a ∈ Z}. Prove that C1 is a subgroup of Z × Z.
(b) Let n ≥ 2 be an integer, and let Cn = {(a, b) | a ≡ b( mod n)}. Prove that Cn is a subgroup of Z × Z.
(c) Prove that every proper subgroup of Z × Z that contains C1 has the form Cn for some positive integer n.
Get Answers For Free
Most questions answered within 1 hours.