1/2+1/6+1/12+1/20+1/30=?
1/2+1/6+1/12+1\20+1/30+1/42+.+1/9900=?
1/2+1/6+1/12+1/20+1/30+1/42+1/56=?
2/1+6/1+12/1+20/1+30/1+42/1+56/1=
2/1+6/1+12/1+20/1+30/1+42/1+56/1=?
1/2+1/6+1/12+1/20+1/30+1/42+1/56=
1+1/2+1/6+1/12+1/20+1/30+1/42=?
1/2,-1/6,1/12,-1/20,1/30
1/2+1/6+1/12+1/20+1/30
1/2+1/6+1/12+1/20+1/30+1/42=?用综合算式
1/2+1/6+1/12+1/20+1/30+.+1/9900=?
简便运算:1/2+(-1/6)+(-1/12)+(-1/20)+(-1/30)+(-1/42)=?
1/2+1/6+1/12+1/20+1/30+……+1/90=?