假设题如何取非

lawyer_1

取非意思就是假如某个选项是错的。

大体有三种情况：

1. all----not all/some---none/always----not always/sometimes----never/everywhere---not everywhere/somewhere---nowhere/only one, exactly one---none, more than one/at least one, some---none

2. 对于选项为条件句，将必要条件取非。

3. 直接将谓语肯定变否定，或否定变肯定。

[此贴子已经被作者于2004-11-4 4:32:38编辑过]

ethyl

好贴！

paopao

谢谢lawyer

leeon

活在当下

能对第二点举个例子吗。

谢谢了。

lawyer_1

if you  get a high score of GMAT, you will be accepted by Harvard University.

取非为：if you  get a high score of GMAT, you will NOT be accepted by Harvard University

hpp920

好贴!!!我还正准备问条件句怎么取非呢, 这回懂了!

活在当下

搞定了。谢谢

Bobbysoft

p->q这个判断(有的称之为命题）从formal logic（形式逻辑)来说，应该是P且~q

if you  get a high score of GMAT, you will be accepted by Harvard University.

It is not the case that if you  get a high score of GMAT, you will be accepted by Harvard University.<=> You get a high score of GMAT and You won't be accepted by Harvard University.

这里的很多说法都和逻辑不同，我补充一下正确的逻辑取非是什么样子的：

~(p或q) <=>(~p)且（~q)

~(p->q)<=>p且~q

~(p且q)<=>(~p)或(~q)

~(p<->q)<=>(p且~q)或（~p且q)

[此贴子已经被作者于2005-3-23 23:16:42编辑过]

livary

顶一下