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Mathematics 17 Online
OpenStudy (anonymous):

what is the supremum of set of real nos???

terenzreignz (terenzreignz):

You know what supremum means?

OpenStudy (anonymous):

yes least uper bound

terenzreignz (terenzreignz):

As a matter of fact, yes. Can we, in fact, *bound* the set of real numbers?

OpenStudy (anonymous):

i think no....but i have read R satisfies the property of completeness

OpenStudy (anonymous):

and according to this property a bounded above set has a supremum

OpenStudy (anonymous):

now what is this???

terenzreignz (terenzreignz):

It means... if a set has an upper bound, then it has a least upper bound (supremum)

terenzreignz (terenzreignz):

The converse is obviously true... If a set has a least upper bound, then it has an upper bound... (proof: duh XD)

terenzreignz (terenzreignz):

So... suppose the set of real numbers has an upper bound..

OpenStudy (anonymous):

then plz tell me what is the sup of R?

terenzreignz (terenzreignz):

Let's suppose there exists a real number a which is the supremum of R.

terenzreignz (terenzreignz):

Then a+1 is also a real number because the set of real numbers is closed under addition.

terenzreignz (terenzreignz):

a < a+1 Which already contradicts the assumption of the EXISTENCE of a supremum.

OpenStudy (anonymous):

what is its upper bound?? infinity??? i think infinity can not be sup

terenzreignz (terenzreignz):

Of course not, infinity is not a number. :D

OpenStudy (anonymous):

then suprimum of R?

terenzreignz (terenzreignz):

Does it even have one?

OpenStudy (anonymous):

what does it mean...i could'nt understand?

terenzreignz (terenzreignz):

Think of it this way... a supremum is like a maximum value...

terenzreignz (terenzreignz):

So... does the set of all real numbers have a maximum?

OpenStudy (anonymous):

yes but this is what i want to ask what is this max no??

terenzreignz (terenzreignz):

Give it a good think... what is the biggest number?

OpenStudy (anonymous):

do you know the ans???

terenzreignz (terenzreignz):

As to what is the biggest number?

OpenStudy (anonymous):

i dont know

OpenStudy (anonymous):

can u tell??

OpenStudy (anonymous):

can u???

OpenStudy (anonymous):

what happens???

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