假设题如何取非

xjlv128

以下是引用Bobbysoft在2005-3-23 23:12:00的发言：

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)

极是极是！但是lawyer-1说的是GMAT的“逻辑”，呵呵，培生要是来严谨的，我们的头岂不是又要大三圈！！

nearmiss

大家好，我是菜鸟。

我想请问一下取非后有什么作用呢，怎么再去判断选项的正确性？

不吝赐教！

dreamchaserdan

引用lawyer的方法，将选项取非，原文结论不成立，则为正确选项。

xjlv128

嗯，是假设题的做法。如果它的反面能导致结论错误，它就不可少，所以是assumption.

amber0919

amber0919

195.

A proposed change to federal income tax laws would eliminate deductions from taxable income for donations a taxpayer has made to charitable and educational institutions. If this change were adopted, wealthy individuals would no longer be permitted such deductions. Therefore, many charitable and educational institutions would have to reduce services, and some would have to close their doors.

The argument above assumes which of the following?

(A) Without the incentives offered by federal income tax laws, at least some wealthy individuals would not donate as much money to charitable and educational institutions as they otherwise would have.

(B) Money contributed by individuals who make their donations because of provisions in the federal tax laws provides the only source of funding for many charitable and educational institutions.

(C) The primary reason for not adopting the proposed change in the federal income tax laws cited above is to protect wealthy individuals from having to pay higher taxes.

(D) Wealthy individuals who donate money to charitable and educational institutions are the only individuals who donate money to such institutions.

(E) Income tax laws should be changed to make donations to charitable and educational institutions the only permissible deductions from taxable income.

Choice A is the best answer, since if this statement is false, all wealthy individuals would, even without the incentive provided by federal tax laws, donate as much money as they do now. In that case, the evidence used in the argument provides no support for the conclusion.

ＯＧ把Ａ取非：at least some---＞all　怎么是这样取的呀？？？　不应该是at least some－－－＞none吗？？

keer1977

at least some wealthy individuals would not donate as much money to charitable and educational institutions as they otherwise would have.

是不是应该这样: none wealthy inviividuals would donate as much money to charitable and educational institutions as they otherwise would have.

amber0919

不能那样取.那样取非结论还是成立的.就应该象OG那样区非:all wealthy individuals would, even without the incentive provided by federal tax laws, donate as much money as they do now.

但我不知道为什么。

numberunique

以下是引用amber0919在2006-4-21 15:37:00的发言：

不能那样取.那样取非结论还是成立的.就应该象OG那样区非:all wealthy individuals would, even without the incentive provided by federal tax laws, donate as much money as they do now.

但我不知道为什么。

all wealthy individuals would

与

none wealthy individuals would not 

不是一样吗

amber0919

谢谢.果然是这样..