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Infinite and finite countable sets 
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#1
Nov2712, 04:29 PM

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Ok I understand the concept of infinite countability and that say the set of all rational #s is infinitely countable, but if I needed to represent the set how do I do that? S={xε rat. # : x= k , k ε a rational #}? that doesn't seem right. Also say I wanted to show a set of finite countable numbers, I'm sure I can just write T={1,2,3,4} but shouldn't i do something more proper and state that T = {n ε rat. # : 1≤n≤4}? I just need help with how to properly represent sets Thanks!



#2
Nov2712, 05:43 PM

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P: 21,215

[QUOTE=hatsu27;4175569] , but if I needed to represent the set how do I do that? S={xε rat. # : x= k , k ε a rational #}? that doesn't seem right. [quote]S = {x : x is rational}. Sometimes Q is used to represent rational numbers, so you could also say S = {x : x ##\in## Q}. 


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