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Mathematics 9 Online
OpenStudy (anonymous):

Prove that there is no smallest positive real number?

OpenStudy (anonymous):

I can divide your number by 2 and get a smaller one.

OpenStudy (anonymous):

lets say your number is a. divide it by a positive number b. a(1/b) keep doing it a(1/b)(1/b) a(1/b)^n will never hit 0 but will keep becoming smaller with every increase in the number of times you divide it.

OpenStudy (skullpatrol):

This the same argument as proving there is no largest positive real number.

OpenStudy (zzr0ck3r):

By archimedes principle: given a<b there is some n in natural s.t. na>b, and given a>0 there is some n in natural s.t. 0 < 1/n < a

OpenStudy (anonymous):

explain it little bit more plz....

OpenStudy (zzr0ck3r):

when proving something you need to show theroems/lemmas/remarks about what you claim....

OpenStudy (zzr0ck3r):

do you know what a natural number is?

OpenStudy (anonymous):

ya

OpenStudy (skullpatrol):

1, 2, 3, 4, ...

OpenStudy (zzr0ck3r):

so you give me any number like: .00000000000000000000001 there is some 1/n that is smaller like 1/10000000000000000000000000000000

OpenStudy (zzr0ck3r):

you could talk about density also, given and real number a<b there is some real number c such that a < c < b let a = 0

OpenStudy (skullpatrol):

What if a=0.999... and b=1 ?

OpenStudy (zzr0ck3r):

add a 9

OpenStudy (zzr0ck3r):

between any two numbers there is an infinite amount of numbers

OpenStudy (skullpatrol):

O.9999...

OpenStudy (zzr0ck3r):

you actually did not show that you added another 9. it would be at the end of your ...

OpenStudy (zzr0ck3r):

:)

OpenStudy (skullpatrol):

There is no end to an endless string of 9s.

OpenStudy (zzr0ck3r):

exactly

OpenStudy (zzr0ck3r):

thus there is always a smaller number

OpenStudy (zzr0ck3r):

or a number inbetween I should say

OpenStudy (skullpatrol):

So there is a number in-between 1 and 0.999...?

OpenStudy (zzr0ck3r):

.9999........ with endless 9's is not a finite number, just like infinity is not a finite number.

OpenStudy (zzr0ck3r):

so you are asking a question that does not make since

OpenStudy (skullpatrol):

1/3 =0.333... is a finite number!

OpenStudy (zzr0ck3r):

1/3 is and the aproximation .33333333333 is an aproximation of 1/3 and yes its finite, but .333333333...... is not a real number if there are infinite 3's

OpenStudy (zzr0ck3r):

we would say it approaches 1/3

OpenStudy (skullpatrol):

2/3=0.6666...

OpenStudy (skullpatrol):

1/3+2/3=1 the last time I checked

OpenStudy (zzr0ck3r):

same thing, if you cant write the number its not finite, and you cant write .666666........(notice you have to do ......)

OpenStudy (zzr0ck3r):

yes, but .333333333+ .6666666666 = .9999999999 != 1

OpenStudy (zzr0ck3r):

you can write .333 untill the universe implodes, it will never be 1/3

OpenStudy (skullpatrol):

http://en.wikipedia.org/wiki/0.999...

OpenStudy (zzr0ck3r):

lol, you are not getting my point. Can you write .333333......?

OpenStudy (skullpatrol):

0.999...=1

OpenStudy (anonymous):

No it doesn't.

OpenStudy (zzr0ck3r):

it approaches 1, and is not finite untill you stop writing the 9

OpenStudy (skullpatrol):

There is no "smallest" number in-between 0.999... and 1.

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