1/4+1/28+1/70+……+1/550(利用裂项)
问题描述:
1/4+1/28+1/70+……+1/550(利用裂项)
答
1/4+1/28+1/70+……+1/550
=1/3×(1-1/4+1/4-1/7+1/7-1/10+...+1/22-1/25)
=1/3×(1-1/25)
=1/3×24/25
=8/25