数学1*2*3的倒数加2*3*4的倒数加3*4*5的倒数...
1/(1*2*3)+1/(2*3*4)+1/(3*4*5)+。。。。。。。。。。。。。+1/n(n+1)(n+2)=
(1/2)*{[1/(1*2)-1/(2*3)]+[(1/(2*3)-1/(3*4)]+[(1/(3*4)-1/(4*5)]+。 。。。。。。。。。。。。+(1/n(n+1)-1/(n+1)(n+2)}=
(1/2)*{1/(1*2)-1/(n+1)(n+2)}=
(1/4)-1/[2(n+1)(n+2)]。
1/(1*2*3)+1/(2*3*4)+1/(3*4*5)+。。。。。。。。。。。。。+1/n(n+1)(n+2)=
(1/2)*{[1/(1*2)-1/(2*3)]+[(1/(2*3)-1/(3*4)]+[(1/(3*4)-1/(4*5)]+。
。。。。。。。。。。。。+(1/n(n+1)-1/(n+1)(n+2)}=
(1/2)*{1/(1*2)-1/(n+1)(n+2)}=
(1/4)-1/[2(n+1)(n+2)]。收起