回复：谢谢Jinjing， 但

来源: 于 2010-03-31 16:58:03 [旧帖] [给我悄悄话] 本文已被阅读：次

I think only use examples: 5-3=2,7-3=4,11-7=4,...,2m+1-(2n+1)=2(m+n)...It is not easy to teach,good lucky.