-1/6 -1/12 -1/20 -1/30…… -1/420等于多少?- 是减号

-1/6 -1/12 -1/20 -1/30…… -1/420等于多少?- 是减号
-1/6 -1/12 -1/20 -1/30…… -1/420等于多少?
- 是减号

-1/6 -1/12 -1/20 -1/30…… -1/420等于多少?- 是减号
=-(1/6+1/12+1/20+1/30……+1/420)
=-(1/2-1/3+1/3-1/4+...+1/20-1/21)
=-(1/2-1/21)
=-19/42

原始=-(1/2-1/3)-(1/3-1/4)-....-(1/20-1/21)=-1/2+1/3-1/3+1/4...-1/20+1/21=-1/2+1/21=-19/42

-1/6 -1/12 -1/20 -1/30…… -1/420
=(-1/2+1/3)+(-1/3+1/4)=......+(-1/20+1/21)
=-1/2+1/21
=-19/42