[分析] Q在(0,1)可數

[pop10353 (卡卡:目)]

Q is countable set
and so Q交(0,1) is countable set

But is it 可列?

if I set Q交(0,1) = {r1,r2,...,r_n,...}

I can find the (r_n+r_n+1)/2 st. it is not all the element

of Q交(0,1)

why??

--
※ 發信站: 批踢踢實業坊(ptt.cc) 
◆ From: 124.9.202.158
推 StellaNe    :可列不一定照大小列 所以(r_n+r_n+1)/2可能為其他元
→ StellaNe    :素
推 gj942l41l4  :不能照大小去列
→ gj942l41l4  :但你可以依分母大小去排它