Question

For which operations is the set {–1, 1} closed?

Choose all answers that are correct.

A.
addition

B.
subtraction

C.
multiplication

D.
division

Answer 1

If I remember what these questions are about, C, and D are correct.
\[-1 \times 1 = -1 \]
\[\dfrac{-1}{1} = -1\]

Negative one is part of the set. Ergo, closed.

Answer 2

so times and subtraction?

Answer 3

Subtraction does not work, since you get 0, and that is not part of the set.

Answer 4

okay so its a c or d we know its c what about addition?

Answer 5

Actually we know it is both, C, and D. Any my bad, with addition we get zero, subtraction gives us -2, which is also not in the set.

Answer 6

okay so its just c d?

Answer 7

Addition:
-1 + 1 = 0.
Subtraction:
-1 - 1 = -2

Answer 8

Yes.

Answer 9

so b c d?

Answer 10

B gives -2, and the set is only {-1, 1} so no.

Answer 11

okay M<# thans