50*51,51*52,52*53.98*99,99*100的倒数和
问题描述：
50*51,51*52,52*53.98*99,99*100的倒数和
答
分数列项
1/(50×51)=1/50-1/51
1/(51×52)=1/51-1/52
.
1/(99×100)=1/99-1/100
原式=1/50-1/51+1/51-1/52+...+1/99-1/100
=1/50-1/100
=1/100