Question

－1/20×21－1/21×22－1/22×23……－1/99×100 求此题的简便方法解题过程,

Answer 1

An=-(n+1)/n=-(1+1/n)Sn=A1+A2+A3+.+An =-(n+1/1+1/2+1/3+...+1/n) = -(n+(1+n)/2) (高一内容)原式=S100-S19 =-301/2+58/2 =-243/2用了一点高一的内容,我现在高二,还能记得就不错了,嘿嘿,快去告诉老师吧,...