作者jore (Light My Fire)
看板GMAT
標題[計量] PP1 PS 176
時間Sat Dec 6 11:53:59 2008
176. 18407-!-item-!-187;#058&011575
If the operation ⊙ is defined for all integers a and b
by a ⊙ b = a + b - ab which of the following statements
must be true for all integers a, b, and c ?
I. a ⊙ b = b ⊙ a
II. a ⊙ 0 = a
III. ( a ⊙ b ) ⊙ c = a ⊙ ( b ⊙ c )
(A) I only
(B) II only
(C) I and II only
(D) I and III only
(E) I, II, and III
ANS: E
有參考過商咖上的解題，但還是看不懂，希望這裡的高人可以幫忙解題
謝謝~
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1F：推 freemind99:這種題目不用想太多 就照題目定義的公式把條件帶進去算 12/06 12:43
2F：→ freemind99:a+b-ab= b+a-ba a+0-ax0=0+a-0xa 12/06 12:44
3F：→ freemind99:(a+b-ab)+c-(a+b-ab)c = a+(b+c-bc)-a(b+c-bc) 12/06 12:46