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Showing posts with label Real Analysis. Show all posts
Showing posts with label Real Analysis. Show all posts

Some important point only for real numbers




1- Denominator of any real number can not be zero.

Y= N/D     D≠0
Hence if denominator is zero then real number can never be possible.
So 1/0, 2/0, 3/0,………..are practically impossible.
i.e.       1/0= undefined.

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Archimedean Property of real numbers



Theorem:- Let a be any real number and b any +ve real number. Then there exists a positive integer n such that
nb>a

Proof:- Given that aϵ R & bϵ R+
So there are two possible cases.
Case 1:- When a≤0
In this case the relation nb>a is always true because the value of nb is always +ve.
Case 2:- When a>0
Let us that there exists no +ve integar such that nb>a
Then we have nb≤a  ⩝  n∈N
It means that a be the upper bound of set S which is given by
S= {b,2b,3b,………..} = {nb:n∈N}.

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Boundness of subsets of R



Upper bound of a subset of R:-

Let S be a subset of real numbers. If there exist a real number K , such that x≤K ⩝ x∈S
Then K is called an upper bound of set S.
If there exists an upper bound for a set S then it is called “bounded above”.
Example:- The set S= {………-4,-3,-2,-1} is bounded above & 9 is an upper bound.

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Archimedean Property of Real Number

Let xxx be any real number. Then there exists a natural number nnn such that n>xnxn>x.
This theorem is known as the Archimedean property of real numbers. It is also sometimes called the axiom of Archimedes, although this name is doubly deceptive: it is neither an axiom (it is rather a consequence of the least upper bound property) nor attributed to Archimedes (in fact, Archimedes credits it to Eudoxus).

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