[高微]請教幾題基本的高微證明

[mathqq (好多問題= =)]

題目如下

1.show that d=inf(S) iff d is a lower bound for S and for any ε>0
  there is an x "屬於"S such that d≧x-ε



  ㄈ:包含於
2.If PㄈQㄈ實數R, P≠ψ, and P and Q are bounded above ,show that supP≦supQ



3.Let Aㄈ實數R and Bㄈ實數R be bounded below and define A+B=｛x+y∣x屬於A and
  y屬於B｝. Is it true that inf(A+B)= infA + infB ?


謝謝大家的幫忙~

--
※ 發信站: 批踢踢實業坊(ptt.cc) 
◆ From: 125.230.68.17
→ koalababy   :這應該是作業吧?!如果是的話，應該要自己想才對