[分析] 兩題集合問題

[u2150260 (鴻哥)]

                                         ∞         ∞
1. Let An=[1-1/n 2+1/n),n=1,2,3...  find ∩An  and  ∪An
                                         n=1        n=1


2. Let a,b be real numbers and b>0. Let An be the interval (a,a+b/n]
                                            ∞
   for every positive integer n .Prove that ∩An is empty set.
                                            n=1

集合的問題答案要怎麼寫呢

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