(1-1/2+1/3-1/4+……+1/19-1/20)/[1/(11×20)+1/(12×19)+……+1/(15×1
(1-1/2+1/3-1/4+……+1/19-1/20)/[1/(11×20)+1/(12×19)+……+1/(15×1
(1-1/2)*(1-1/3)*(1-1/4)*(1-1/5)*(1-1/6)*…*(1-1/19)*(1-1/20)=
1/10×11+1/11×12+…+1/19×20
1/(12×13)+1/(13×14)+……+1/(19×20)等于多少
简算1/(2×3)+1/(3×4)+1/(4×5)+……+1/(18×19)+1/(19×20)
1*1/2+1/2*1/3+1/3*1/4……1/19*1/20
1+3+5+7+……+19+(-2)+(-4)+(-6)+(-8)+……+(-20)
算式(3/1-4/1)+(4/1-5/1)……+(20/1-19/1)求解
-1/10×11-1/11×12-1/12×13—……—1/19×20
-1/10*11-1/11*12-1/12*13-……-1/19*20
1/1*2*3+1/2*3*4+……+1/18*19*20
|1/10-1/11|+|1/11-1/12|+…|1/19-1/20|