In: Advanced Math
Which of the following are groups? + And · denote the usual addition and multiplication of real numbers.
(G, +) with G = {2 n | n ∈ Z},
(G, ·) with G = {2 n | n ∈ Z}.
Determine all subgroups of the following cyclic group
G = {e, a, a2, a3, a4, a5}.
Which of these subgroups is a normal divisor of G?