Answers to Exercises
Exercise 1
Parts B and D are not functions.
Exercise 2
No, this is not a field. ⟨ℝ, −⟩ is not an Abelian group; subtraction is not commutative.
Parts B and D are not functions.
No, this is not a field. ⟨ℝ, −⟩ is not an Abelian group; subtraction is not commutative.