A set is closed under multiplication if for any two elements, x and y, in the set, their product, x*y, is also a member of the set.
Yes.
yes
Yes
The numbers are not closed under addition because whole numbers, even integers, and natural numbers are closed.
Is { 0, 20 } closed under multiplication
No.
No.
No.
Yes they are closed under multiplication, addition, and subtraction.
Rational numbers are closed under addition, subtraction, multiplication. They are not closed under division, since you can't divide by zero. However, rational numbers excluding the zero are closed under division.
Yes!
Yes!
Yes.
Yes.
A set is closed under multiplication if for any two elements, x and y, in the set, their product, x*y, is also a member of the set.
Yes.