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

more than 1

Answer 2

@paki

Answer 3

I think you may need to review what closed under an operation means.

1 + 1 = 2, which isn't in the set. Therefore we can get outside of the set by adding elements. When we can do this, it isn't closed under addition.

1 - (-1) = ?
1 / 0 = ?

As it turns out, of those four operations, the set is only closed under multiplication

Answer 4

does that help any?

Answer 5

@lilshane