※ 引述《surfingdream (GMATing)》之銘言：
: 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
: III)(a@b)@c =a@(b@c)
: 請問一下上面這個怎麼算出來是true
: 感謝
原式a@b=a+b-ab
(a@b)@C=a+b-ab+c-c(a+b-ab) =a+b+c-ab-ac-cb+abc
^^^^^^ ^ ^^^^^^^^^
表a b ab
(b@c)=b+c-bc
a@(b@c)=a+b+c-bc-a(b+c-bc) =a+b+c-bc-ab-ac+abc
^ ^^^^^^ ^^^^^^^^^
表a b ab
故成立
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 61.229.106.6
推
01/18 12:09, , 1F
01/18 12:09, 1F
推
01/18 13:27, , 2F
01/18 13:27, 2F
討論串 (同標題文章)