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题库 / Prep2007E1-DS-178
If there are more than two numbers in a certain list, is each of the numbers in the list equal to 0 ?
(1) The product of any two numbers in the list is equal to 0.
(2) The sum of any two numbers in the list is equal to 0.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
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2） sum of any=0 1+-1=0 但是1和别的数加起来不能=0，所以（2）使得所有数字只能是0
It's also possible one number to be different from 0 and all other numbers to equal to 0 (in this case the product of ANY two numbers in the list will also be equal to 0). For example, {0, 0, 1} --> answer NO.
这里强调任意！！就是每个数都是零（2）不存在 -1，1，-2，2 因为不是任意两个相加都等于0
那就有两个数不等于0，别的0和这两个数相加就不会为0
比如只有三个数，-1，1和0，不能保证除-1和1相加为零后，其他的数相加也为0登录 或 注册 后可以参加讨论