I need help with the Closure Property, i dont understand my homework.?

Question

Hi, i was wondering if someone could plz help me with the Closure Property in math. I really dont know what it is. Heres the ? on my homework::

The Closure Property states that because the sum or product of two whole numbers90,1,2,3, ...) is also a whole number, the set of whole numbers is closed under + and x. Tell whether the set of whole numbers is closed under subtraction and division.If not, give counterexamples.

Dont get it! :( HELP PLZ

Answer 1

closure means you did not step out of the set after doing an operation.

As you said, If you add any two whole numbers you always get a whole number. Same with multiplication.

   But if we subtract  2 whole numbers you may not get a whole #.  

7 - 9 = -2 and -2 is NOT a whole number( it is an integer)

likewise 7/9 = is NOT an integer.

a good example to think about is Even numbers, the sum or product of two even numbers is Even, so Even numbers are closed under addition or multiplication.

  Odd numbers are not closed under addition ( 7 - 3  = 4 ) but are closed under multiplication