The set of rational numbers Q ⊂ R is neither open nor closed. It isn't open because every neighborhood of a rational number contains irrational numbers, and its complement isn't open because every neighborhood of an irrational number contains rational numbers.
Irrational numbers are not closed under addition, subtraction, multiplication, and division.
Closure property under multiplication states that any two rational numbers' product will be a rational number, i.e. if a and b are any two rational numbers, ab will also be a rational number.
The algebraic closure A of Q is the field of algebraic numbers, which consists of those complex numbers which are roots of some non-zero polynomial in one variable with rational coefficients. It is a countable set and therefore A⊊C.
Closure property For two rational numbers say x and y the results of addition, subtraction and multiplication operations give a rational number. We can say that rational numbers are closed under addition, subtraction and multiplication. For example: (7/6)+(2/5) = 47/30.
It suffices to show that for every real number r and every ϵ>0, there is at least one rational q which is "ϵ-close" to r (that is, |r−q|≤ϵ), since this will show that every open ball around r contains a rational. This shows that the complement of Q has empty interior, so the closure of Q is all of R.
The closure property of addition states that when any two elements of a set are added, their sum will also be present in that set. The closure property formula for addition for a given set S is: ∀ a, b ∈ S ⇒ a + b ∈ S.
Closure property of rational numbers under subtraction: The difference between any two rational numbers will always be a rational number, i.e. if a and b are any two rational numbers, a – b will be a rational number.
Conclusion. It is evident that rational numbers can be expressed both in fraction form and decimals. An irrational number, on the other hand, can only be expressed in decimals and not in a fraction form. Moreover, all the integers are rational numbers, but all the non-integers are not irrational numbers.
Conclusion. It is evident that rational numbers can be expressed both in fraction form and decimals. An irrational number, on the other hand, can only be expressed in decimals and not in a fraction form. Moreover, all the integers are rational numbers, but all the non-integers are not irrational numbers.