详细问题描述及疑问:期待您的答案,希望你能感受到,我最真诚的谢意 !
本页链接:http://www.oxrm.com/question/1694876279211048
-1?+2?-问3?+4?-……助+n?=(2?-1?)+(4?-3?+(6?-5?)+……+[n?-(n-1)?]=(2-1)(含次2+1)+(4-3)(4+3)+(6-5)(6+5)+……+[n-(n-1)][n+(n-1)]=(2+1)+(4+3)+(6+5)+……+[n+(n-1)=1+2+3+……+n=含简伤研选依结继n(n+1)/2