[求助]MATH D.S.

yahoo750

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]

孤注一掷

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.

chenwu77

can we have same number twice in this set?

yahoo750

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!

passerr

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。

passerr

sorry,这里的“不确定”指“不充分”。

yahoo750

Thanks a lot!