math
posted by b6 on .
Which set of integers is not closed under what operation?
+

x
Division
I thought it was division but I don't understand , can you please explain this.
Thanks

Think of it this way:
If you add two integers, will you always get back an integer ? YES , so it is closed under addition
if you divide two integers will you always get back an integer.
e.g. 6 รท 4 = 1.5 , which is NOT an integer
so not closed under division
make a similar test for subtraction and multiplication.
What do you think? 
6*4=24 it is an integer=closed for mult.
107=3 so it is also an integer
Thanks