can not / can't點樣取決來用? 係咪一個人就用can't兩個人用can not?

Both have the same meaning. Usually, use short form (can't) during conversation and the other in written form.

Can't is the short form of cannot
when we are writing formal letter, we should use "cannot", otherwise using "can't" is acceptable.
SO, both of your sentence are correct, but you can use:
1) you cannot talk in the library
2) they can't talk in the library

can not and can't is equal
but if you writing a letter you need use can't is not can not

"Can't"其實即是"Can not",只不過它通常用於口語.

can not = can't
2個一樣, can't 係 can not 0既縮寫

can not is can't

無分別架喎!!
個分別就係 it is 同 it's﹐I will 同 I'll 一樣
只不過係簡寫咋!!

我喺美國住左十年都唔知﹐唔通連我D鬼仔friend 都錯??

CAN NOT = CAN'T

CAN'T 只係CAN NOT 的簡寫....意思同埋用法都係完全相同的!

2007-09-30 03:33:05 補充：
如果用正寫唔用簡寫, 可以係加強用意的!1) you can't talk in the library

2007-09-30 03:33:45 補充：
1) you can't talk in the library

2007-09-30 03:34:19 補充：
1)語氣較輕, 2)語氣較重!

是，) you can't talk in the library
2) they cannot talk in the library
!

can't=cannot根本就一樣~~~