1/4+1/28+1/70+……+1/8554 怎么计算,
问题描述：
1/4+1/28+1/70+……+1/8554 怎么计算,
答
1/4+1/28+1/70+……+1/8554
=1/1*4+1/4*7+1/7*10+.1/(91*94)
=1/3*(1-1/4)+1/3(1/4-1/7)+1/3(1/7-1/10)+...+1/3(1/91-1/94)
=1/3(1-1/4+1/4-1/7+1/7-1/10+.+1/91-1/94)
=1/3(1-1/94)
=1/3*93/94
=31/94