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An ESL Learner
Lv 7
An ESL Learner asked in 科學及數學數學 · 9 years ago

假設 P，P ⇒ Q 及 Q ⇒ R，但同時 ~R。那麼我們

假設 P，P ⇒ Q 及 Q ⇒ R，但同時 ~R。那麼我們除了求出 ~P 外，還可不可以求出 ~Q 呢？

Update:

萬分感謝。

3 Answers

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  • myisland8132
    Lv 7
    9 years ago
    Favorite Answer

    P﹐P ⇒ Q 及 Q ⇒ R 和 ~R 是 T

    R是F => Q是F。因若不然﹐Q是T而R是F則 Q ⇒ R也是F﹐矛盾。

    因此~Q是T。

  • frankwoodtiger
    9 years ago

    Since ~R is true. Then, the contrapositive of Q ⇒ R is ~R ⇒ ~Q.

    Then, we can get ~Q.

  • Ling shan
    9 years ago

    可以 ok !! 可以求出 ~Q

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