请教PP1-DS的两题,搞不懂~

loveshin86

178.  17649-!-item-!-187;#058&011192

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.

答案:B..我的疑问是A为何成立呢?

148.  14854-!-item-!-187;#058&010192

In the xy-plane, does the line with equation y = 3x + 2 contain the point (r, s) ?

 

(1)  (3r + 2 - s)(4r + 9 - s) = 0

 

(2)  (4r - 6 - s)(3r + 2 - s) = 0

答案:C...疑问是A.B.不是都各自能算出r.s吗?为什么要合在一起才能解呢?

请高人指点,拜托~

misskangta

偶不是高人，小N也不是，不过题目偶都做过，偶来解释一下吧。呵呵
第一道是想问A为什么不行吧？举个例子，0，0，2这个LIST就不行

第二道一定要2项合起来，否则R和S的值不唯一