Question

List all subgroups of (Z15,+)

Answer 1

isnt it the same as the prime factorization of 15? i forgot how to make the tree tho so thats prolly not accurate

Answer 2

or is it residual groups?

Answer 3

closure, associativity, identity and inverse have to be included, so im thinking along the lines of
\[Z_{15}/Z_{1}\]
\[Z_{15}/Z_{3}\]
\[Z_{15}/Z_{5}\]
\[Z_{15}/Z_{15}\]

Answer 4

I think amistre64 is correct.

https://en.wikipedia.org/wiki/Fundamental_theorem_of_cyclic_groups