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标题: [求助]MATH D.S. [打印本页]

作者: yahoo750    时间: 2003-1-20 23:30     标题: [求助]MATH D.S.

If S an infinite set of real numbers, is there a numver in S that is less than every other number? 1)every number is a interger 2)every number is positive
Could anyone help me? I've chosen E as a correct answer. The examples are 222222~this kind of set of numbers and 123456~this kind of set of numbers. But the correct answer is C. I dont't know why![em08]
作者: 孤注一掷    时间: 2003-1-20 23:43

According to the 2 condidtions, the numbers in the set S are positive integers, and now you should be able to tell the smallest number is 1. So choice C is correct.
作者: chenwu77    时间: 2003-1-21 01:14

can we have same number twice in this set?
作者: yahoo750    时间: 2003-1-21 12:08

Thank you.  In the set S for example 222222~,the answer is no, but in set S for example 12345~,the answer is yes. So there isn't a universal answer to the question. I also take for granted the E is the correct answer. Could you give me more concrete explanation, please!
作者: passerr    时间: 2003-1-21 13:38

C.
(1)整数集中有负整数、0和正整数,但无法确定最小的负整数。故(1)不确定。
(2)正数集。因S是实数,同样无法确定最小的正数。故(2)不确定。
(1)+(2),最小的正整数是1。故答案为C。
作者: passerr    时间: 2003-1-21 14:00

sorry,这里的“不确定”指“不充分”。
作者: yahoo750    时间: 2003-1-22 21:15

Thanks a lot!




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