Re: [問題] GWD數學問題
※ 引述《htbk (小小艾佛森)》之銘言：
: If n is a positive integer and r is the remainder
: when (n-1)(n+1) is divided by 24, what is the value of r?
: (1) 2 is not a factor of n.
: (2) 3 is not a factor of n.
: 答案是 : C
: 遇到這種題目
: 我真的不太會判斷.......請教高手幫我指點一下
: 這題基本題目的觀念
(1) set n = 2k + 1
m = (n-1)(n+1) = (2k)(2k+2) = 4(k)(k+1)
=> m為8的倍數 (X)
(2) set n = 3k + 1
m = (n-1)(n+1) = 3k(3k+2)
=> m為3的倍數 (X)
(1+2) m為24的倍數
=> r = 0
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