Question

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

(im not great at math, but please dont straight up give me the answer, I do want an education lol.)

Answer 1

Whoops, the choices are:
A.


addition


B.


subtraction


C.


multiplication


D.


division

Answer 2

wait i don't get this, what are you supposed to do?

Answer 3

Choose all the answers that apply to the given numbers

Answer 4

ok so.... the numbers are -1 and 1, but there is nothing else... how is addition, subtraction, multiplication. or division relate to those two numbers?

Answer 5

For a set to be closed under an operation, that means you take any two elements and perform the operation you should get another number that is in the same set.

So let's claim that {-1, 1} is closed under addition.

This claim is false because -1 and 1 are elements of the set but -1+1 = 0 is NOT part of the set. The element 0 is outside the set so it's like there is a hole (preventing it from being closed). This is how I remember what closed means.

Answer 6

hence just multiplication and division satisfy the closed property
since you have 2 elements -1, 1
multiplication (-1)*(1) =-1 , the result is in the given set also.
check the rest by (-1)(-1) =1 , in the set also
(1)(1) =1 , in the set
so multiplication holds.
the same with division.

Answer 7

Ah, ah, ahh. Damn you 7th grade Math for being so complicated. Thank you both for putting it into /human/ terms :)