-1/10*11-1/11*12-1/12*13-……-1/19*20

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-1/10*11-1/11*12-1/12*13-……-1/19*20
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-1/10*11-1/11*12-1/12*13-……-1/19*20
-1/10*11-1/11*12-1/12*13-……-1/19*20

-1/10*11-1/11*12-1/12*13-……-1/19*20
原式=-(1/10*11+1/11*12+1/12*13……+1/19*20)
=-(1/10-1/11+1/11-1/12+1/12-1/13……+1/19-1/20)
=-(1/10-1/20)
=-1/20

原式=-1*（1/10 -1/11 +1/11 -1/12 +……1/19-1/20）=-1*(1/10-1/20)=-1/20

-1/10*11-1/11*12-1/12*13-……-1/19*20
=-(1/10*11+1/11*12+1/12*13+..+1/19*20)
=-(1/10-1/11+1/11-1/12+1/12-1/13+...1/19-1/20)
=-(1/10-1/20)
=-1/20

可把1/(10*11)拆成1/10-1/11,这两个是相等的，后面同理，可一一约掉，只剩头尾

拆项相消
原式=-（1/10-1/11+1/11-1/12+1/12-1/13……+1/19-1/20）
=-(1/10-1/20)
=-1/20

1+10-11+12-1? -1/(10*11)-1/(11*12)-...-1/(99*100) 1/10*11+1/11*12+...+1/19*20=? 1/10*11+1/11*12+.+1/59*60 1/10×10+1/11×11+1/12×12+...+1/999×999+1/1000×1000 1/10*11+1/11*12+1/12*13+1/13*14+1/14*15等于? 9*10/1+10*11/1+11*12/1+12*13/1怎么算（简算） 1/9*10+1/10*11+1/11*12+1/12*13.1/100*101= 求|10/1-11/1|+|11/1-12/1|+.+|49/1-50/1|的值 |1/11-1/10|+|1/12-1/11|+……+|1/100-1/99| 求|1/10-1/11|+|1/11-1/12|+.+|1/49-1/50|的值 |1/10-1/11|+|1/11-1/12|+…|1/19-1/20|急 求|1/10-1/11|+|1/11-1/12|+…+|1/49-1/50|RT 求1/10-1/11+1/11-1/12+……+1/49-50--1/50 |1/11-1/10|+|1/12-1/11|+|1/13-1/12|-|1/13-1/10|=? (9+10+11/8-10+11+12/9+11+12+13/10-12+13+14/11)/(1/8-1/9+1/10-1/11)=? (1/8+1/9+1/+1/10+1/11)*(1/9+1/10+1/11+1/12)-(1/8+1/9+1/10+1/11+1/12)*(1/9+1/10+1/11) 计算,(1/8+1/9+1/10+1/11)x(1/9+1/10+1/11+1/12)-(1/8+1/9+1/10+1/11+1/12)x(1/9+1/10+1/11)