奥数:1/2+1/6+1/12+1/20+1/30+1/42+1/56 =
问题描述:
奥数:1/2+1/6+1/12+1/20+1/30+1/42+1/56 =
答
原式=1/1×2+1/2×3+……+1/6*7+1/7*8
=1-1/2+1/2-1/3……+1/6-1/7+1/7-1/8
=7/8