division
No, the natural numbers are not closed under division. For example, 2 and 3 are natural numbers, but 2/3 is not.
yes
Yes, but only when the denominator is non-zero. Division by 0 is not defined.
The set of rational numbers is closed under all 4 basic operations.
There cannot be a counterexample since the assertion is true. This requires you to accept the true fact that the terminating decimal 1.25, for example, is equivalent to the repeating decimal 1.25000... (or even 1.24999.... ).
no
In fact, the statement is true. Consequently, there is not a proper counterexample. The fallacy is in asserting that a terminating decimal is not a repeating decimal. First, there is the trivial argument that any terminating decimal can be written with a repeating string of trailing zeros. But, Cantor or Dedekind (I can't remember which) proved that any terminating decimal can also be expressed as a repeating decimal. For example, 2.35 can be written as 2.3499... Or 150,000 as 149,999.99... Thus, a terminating decimal becomes a recurring decimal. As a consequence, all real numbers can be expressed as infinite decimals. And that proves closure under addition.
You can give hundreds of examples, but a single counterexample shows that natural numbers are NOT closed under subtraction or division. For example, 1 - 2 is NOT a natural number, and 1 / 2 is NOT a natural number.
There is no counterexample because the set of whole numbers is closed under addition (and subtraction).
no, but is a hard question 4 some 1 like me who is young....... thanks 4 asking! (:
-3 is a negative integer. The absolute value of -3 is +3 which is not a negative integer. So the set is not closed.
2 = 2/1 is rational. Sqrt(2) is not rational.
-2 - (-5) = -2 + +5 = +3. (+3 is not in the set of negative numbers.)
They are closed under all except that division by zero is not defined.
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.
division