一个等差数列与一个等比数列对应项的积构成的新数列{a_n},其通项an可表示为a_n=(an+b)·q~(n-1)(a,b不同时为0,q≠1).求这个数列的前n项和Sn时,一般想到利用错位相减的方法,但当an+b或q是一个较复杂的表达式时,很容易出现计算错误,此时不妨试试裂项求和的方法.我们先看一个实例.例1已知数列{a_n}的通项,求其前n项和. A new sequence {a_n} formed by the product of a sequence of equal-difference sequences and an equal-number sequence can be expressed as a_n = (an + b) · q ~ (n-1) 0, q ≠ 1). When finding the first n terms and Sn of this series, we generally think of using the method of dislocation subtraction. However, when an + b or q is a more complex expression, it is easy to make a calculation error Let’s take a look at an example. Example 1 We know the general term of {a_n} and find the first n terms and.