Question

The set S consists of all odd multiples of 3: S = {..., -9, -3, 3, 9,...}. If the integers x and y are in S, then which of the following must also be in S?
A) xy
B) x + y
C) x - y
D) x/y
E) -x - y

Explain too, thanks.

Answer 1

I think it is gonna be xy

because if ur set contains all odd multiples of 3 (-9,-3,3,9,15,21,27...
and u pick any 2 of those numbers and multiply them u will end up with an odd numbered multiple of 3

and if u pick out any 2 numbers in ur set..and do any of the other things in ur answer choices, it will not always be an odd numbered multiple of 3