→ suhorng :不太懂 要有個F closed but not bounded很容易 04/16 00:12
→ suhorng :但是 F 交集 K 一定 bounded 04/16 00:12
→ suhorng :R^n就是closed 04/16 00:12
→ suhorng :{m|m是整數} 也是closed 04/16 00:13
推 gj942l41l4 :加油 04/16 00:21
→ hotcom :搞不太懂 為何{m│m是整數}為closed？ 04/16 00:23
推 gj942l41l4 :從定義下手吧 因為它的補集是open 04/16 00:27
→ suhorng :同上 closed<=>補集open<=>包含所有limit pts 04/16 00:32
→ suhorng :直觀圖形上 "要包含所有邊界" 04/16 00:33
→ hotcom :因為R^N上，F is closed 和 K is compact 04/16 00:51
→ hotcom :所以必集合的任意交集必為必集合，且K帶有bound性質 04/16 00:52
→ hotcom :故F交集K必然為closed and bounded故可推出其compact 04/16 00:52
→ hotcom :? 04/16 00:52
推 herstein :YES 04/16 00:56
→ suhorng :是 04/16 00:56
推 thisday :隊 04/16 00:56
→ hotcom :喔喔喔~~燃起一線生機...現在來看2.2..ˊ_ˋ 04/16 00:58
→ hotcom :看不懂第三題問 if x/y 的意思.... 04/16 01:38
推 herstein :應該是x不等於y的符號只是這張印刷不清楚 04/16 02:06
→ hotcom :恩，我寄信給老師了，看他怎樣回 04/16 02:11
→ hotcom :直立版本的原卷，剩下2,3,6求指點 Or2 04/16 02:12
→ hotcom :3 done ^_^ 04/16 02:29
→ hotcom :有人能教我6.2怎證嗎？寫到剩下這題了 04/16 11:39
→ forloricever:取個d(y, x_n)->inf_x in C d(y, x_n),再用連續, 04/16 12:22
→ forloricever:Sequentially compact 04/16 12:22
→ forloricever:證 x_n 有 subsequence 收歛 04/16 12:26
推 mathphysics :請問你的命題是R^N版本 還是一般metric space的命題 04/17 00:29
→ mathphysics :版本? 04/17 00:29
→ hotcom :R^N 04/17 00:37
→ sneak : //noxiv.com 11/10 11:40
→ muxiv : //noxiv.com 07/07 10:53