标题: OG11-綠DS83 [打印本页] 作者: Kath1985 时间: 2010-3-30 15:22 标题: OG11-綠DS83 If K and n are integers, is n divisible by 7 ? 1 n-3=2k 2 2k-4 is divisible by 7 答案C 想請問條件1和條件2要怎麼合併判斷 ? OG寫著n=2k+3 from (1) can be expressed as n=2k-4+7 實在看不懂 作者: tonyweng 时间: 2010-3-30 17:26
n=2k+3=（2k-4）+7 条件2可得2k-4能被7整除， 所以n能被7整除
