Which equations show that the set of whole numbers is closed under addition?

Choose all answers that are correct.

A.
0 + (–1) = –1

B.
1 + 1 = 2

C.
2 + 0 = 2

D.
2 + (–1) = 1

Question

Which equations show that the set of whole numbers is closed under addition?
 
Choose all answers that are correct.
 
 A.
0 + (–1) = –1
 
 B.
1 + 1 = 2
 
 C.
2 + 0 = 2
 
 D.
2 + (–1) = 1

anonymous · Answer

@Michele_Laino

michele_laino · Answer

are Whole numbers with or without sign?

anonymous · Answer

with out?

michele_laino · Answer

for example Whole numbers are in this set?
$$\mathbb{N} $$
or in this set
$$\mathbb{Z}^+ \cup \mathbb{Z}^- \cup {0}$$

anonymous · Answer

???

michele_laino · Answer

sorry, what do you means with "Whole numbers"?
Usually I mean numbers which belongs to $$\mathbb{N} $$

anonymous · Answer

What???

anonymous · Answer

so Whole Numbers can have sign?

michele_laino · Answer

conjecture:
if Whole numbers are numbers which belong to set $$\mathbb{N} $$
then your answers are B. and C.