1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+.1/9900=?
问题描述：
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+.1/9900=?
答
裂项法
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+.1/9900
=1-1/2+1/2-1/3+1/3-1/4+.+1/99-1/100
=1-1/100
=99/100