2分之一加6分之一加12分之一.

1/2+1/6+1/12+...+1/110 =(1-1/2)+(1/2-1/3)+(1/3-1/4)+...+(1/10-1/11)
=1-1/11
=10/11

1/2+1/6+1/12+……+1/110=
1-1/2+1/2-1/3+1/3-1/4+……+1/10-1/11=
1-1/11=10/11

原式=1/(1*2)+1/(2*3)+1/(3*4)+......+1/(10*11)=(1-1/2)+(1/2-1/3)+(1/3-1/4)+......+(1/10-1/11)=1-1/11=10/11

10/11
不会错的
1/2+1/6+1/12+……+1/110=
1-1/2+1/2-1/3+1/3-1/4+……+1/10-1/11=
1-1/11=10/11

1/2+1/6+1/12+......+1/110=(1-1/2)+(1/2-1/3)+(1/3-1/4)+......+(1/10-1/11)=1-1/11=10/11
1/n(n+1)=1/n-1/n+1

1/2x3+1/3x4+.............+1/10x11
不知道你看不看得懂。

1/2+1/6+1/12+......+1/110
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+......+(1/10-1/11)
= 1-1/2+1/2-1/3+1/3-1/4+......+1/10-1/11
=1-1/11
=10/11

1/2+1/6+1/12+...+1/110
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+...+(1/10-1/11)
=1-1/11
=10/11

第4个数是什么？