Answers

2014-06-03T17:58:51+08:00
{1,2,3,...} - this is an example of indefine set - it can have infinite elements.

Define set is closed, for example:
{1,2,3}
{green, blue, red}
{a,f,b,n,p}
{-1,-2,0,1,2}
{Math, Physics, Chemistry}
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