Basic Logic (Logic 高手幫幫手)

2012-02-21 4:50 am

let P(x) denote the statement "x is an accountant" and Q(x) denote the statement "x owns a Porsche". Write the following symbolic form:

1) Some accountant owns a Porsche.
個答案係there exist at least one x such that, P(x) and Q(x)
呢句既意思係唔係最少有一個人是accountant 和最少有一個人 owns a Porsche?但咁樣既話好似分開左2個唔同既人,一個是accountant,另外一個owns a Porsche...

點解唔係there exist at least one x such that, P(x)-->Q(x)?
呢句意思係唔係最少有一個人是accountant, 他owns a Porsche?

回答 (1)

hung

2012-02-21 5:37 am

✔ 最佳答案

1: 個答案既意思係最少有一個人(x) , 佢係 accountant 同時 owns a porsche . (p & q)而你果句的確係冇要求x_0同x_1 係同一個人, 你果句可寫成 : there exist x_0 , x_1 , such that p(X_0) and q(x_1)
2. there exist at least one x such that, P(x)-->Q(x) 可以睇成
存在一個人, 若果佢係accountant , 佢就owns a Porsche .

( * p 可以係false , 因為當~p 係true , q 係false 既時候 p=>q 都係true)
即係2. 中間果句"若果"所指既人可以唔存在

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