I am reading Dummit and Foote on Ring Theory - ch 7
On page 228 D&F give examples of subrings
For example 2 they write
" is a sub-ring of as is for any integer n.
The ring is not a subring of for any "
My question is surely the ring is a subring of if we identify the equivalence class with 0 and with 1
Perhaps the point D&F are making is that 0 and 1 are not the same as and ?
Can someone help by clarifying this issue