用你的发现来计算1/2+1/6+1/12+1/20=?
追答用公式逆向法:1/(n*(n+1))=1/n-1/(n+1)可得
1/2+1/6+1/12+1/20=(1/1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5
=1-1/5
=4/5
用你的发现来计算1/2+1/6+1/12+1/20=?
追答1/2+1/6+1/12+1/20=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5=4/5