![Rank: 4](images/default/star_level3.gif)
- 精华
- 0
- 积分
- 620
- 经验
- 620 点
- 威望
- 61 点
- 金钱
- 61 ¥
- 魅力
- 61
|
求助 OG13 DS136
136. If° represents one of the operations +,•-, and x, is
k°(£ +m) =(k ° £)+(k ° m)for all numbers k,£,
andm?
(1) k ° 1is not equal to 1 ° k for some numbers k.
(2) ° represents subtraction.
(1) For operations + andX, k ° 1is equal to
1 ° k since £ + l = l + /£and>£xl = lx/i
Therefore, the operation represented
must be subtraction. From this, it
is possible to determine whether
QQ:1014347461制作
k-(£ +m) =(k-£) +(k-m) holds for all
numbers k, £, and m; SUFFICIENT.
(2) The information is given directly that
the operation represented is subtraction.
Once again, it can be determined whether
k-(t +m) = (k-e) +(k-m) holds for all
numbers k, £, and m; SUFFICIENT
为什么减号可以hold for all numbers
感觉减号的话只能是k=0才成立了
谢谢! |
|