关于有限数列的求和问题,在高中数学课本内只介绍了两种基本数列——等差数列和等比数列的求和公式.然而,我们经常碰到一些数列,这些数列既不是等差数列,也不是等比数列,求它们的前n项之和是困难的.利用拆项相消法可求某些数列的前n项之和. With regard to the summation of finite sequences, only two basic sequences are introduced in mathematics textbooks for high schools: sum formulas for arithmetic sequences and geometric sequences. However, we often encounter sequences that are not equal arithmetic sequences. Nor is it equal to a sequence of numbers, and it is difficult to find the sum of the first n terms. Using the decomposing term destructive method, we can find the sum of the first n terms of some series.