1/2+1/6+1/12+------+1/9900
=1/1*2+1/2*3+1/3*4+------+1/99*100
=1-1/2+1/2-1/3+------+1/99-1/100
当中抵消光了
=1-1/100
=99/100
这叫做裂项相消.
多谢!