题目表示错了.
1/(1*5)+1/(5*9)+1/(9*13)+……+1/（97*101）
=1/4*(1-1/5+1/5-1/9+1/9-1/13+……+1/97-1/101)
=1/4*(1-1/101)
=1/4*100/101
=25/101 .