数列与数列相结合的综合题这类综合题主要考查等差数列和等比数列的定义、通项公式、前n项和公式以及性质等内容.例1已知Sn是数列｛an｝的前n项的和,a1=1,Sn+1=4an+2,n=1,2,3,4,…(1)设bn=an+1-2an(n=1,2,3,4,…),求证:数列｛bn｝为等比数列.(2)设cn=2ann(n=1,2,3,4,…),求证: The comprehensive problem of the combination of series and sequence is mainly to examine the definition of the arithmetic sequence and geometric sequence, the general formula, the first n terms, the formula, and the properties. Example 1 It is known that Sn is the front of the sequence {an}. The sum of n items, a1=1, Sn+1=4an+2, n=1,2,3,4,... (1) Let bn=an+1-2an(n=1,2,3,4, ...), Prove that: The sequence {bn} is an equal number sequence. (2) Let cn=2ann(n=1,2,3,4,...), verify: