2∕3＋14／15＋34／35＋62／63＋98／99＋142／143
=6-(1/3+1/15+1/35+1/63+1/99+1/143)
=6-1/(5-3)×(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13)【裂项法,什么叫分裂啊】
=6-1/2×12/13
=6-6/13
=72/13(5又7/13)