Exercise
Let (R,+,*,0,1) be a ring. Does it make sense to talk about the element -5?
That depends on R.
No.
Yes.
Wrong.
Alas, not the right answer.
Indeed,
-5 = (-1)+(-1)+(-1)+(-1)+(-1) = -(1+1+1+1+1).
Exercise
Let (R,+,*,0,1) be a ring. Does it make sense to talk about the element -5?
That depends on R.
No.
Yes.