1/1*2+1/2*3+1/3*4+1/4*5+------+1/99*100
问题描述：
1/1*2+1/2*3+1/3*4+1/4*5+------+1/99*100
要用拆项相消法帮忙看看
答
1/1*2+1/2*3+1/3*4+1/4*5+------+1/99*100
=1-1/2+1/2-1/3+1/4-1/5+……+199-1/100
=1-1/100
=99/100