1/2 - 1/6 - 1/12 - 1/20 - 1/30 - 1/42 - 1/56怎么算

1/2+1/6+1/12+1/20.+1/380 2%1+6%1+12%1+20%1+30%1 1/2+1/6+1/12+1/20+1/30 1/2-1/6-1/12-1/20-...-1/110 1/2,-1/6,1/12,-1/20,1/30 2/1+6/1+12/1+24/1+48/1 1/2+1/6+1/12+1/20+.1/90 2/1+6/1+12/1+20/1+...+2450/1 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72 1+1/2+1/12+1/6+1/20+1/30+1/40+1/56 (1-1/2)+(1-1/6)+(1-1/12)+...+(1-1/110)=? 1/2+1/6+1/12+...+1/4054182 等于多少? 1/2+1/6+1/12+...+1/56=快 1/2+1/6+1/12+1/20= 1/2+1/6+1/12+.1/9900 1/2+1/6+1/12+.+1/9900 1/2+1/6+1/12+...+1/72简便运算