一、样题
二、裂项
1、两个相邻数裂项
2、两个不相邻数裂项
练习
1 1 ∗ n + 1 n ∗ ( n + m ) + 1 ( n + m ) ∗ ( n + 2 m ) + . . . + 1 ( n + 9 m ) ∗ ( n + 10 m ) = \frac{1}{1*n}+\frac{1}{n*(n+m)}+\frac{1}{(n+m)*(n+2m)}+...+\frac{1}{(n+9m)*(n+10m)}= 1∗n1+n∗(n+m)1+(n+m)∗(n+2m)1+...+(n+9m)∗(n+10m)1=