I. Selection (5 points× 7 = 35 points):

1 and 56 are () terms of the sequence {n2+3n+2}.

a、6 B、7 C、8 D、9

2, in series,, then = ()

a、25 B、 13 C、23 D、 12

3. In arithmetic progression {an}, the sum of the first four items is 1, and the sum of the first eight items is 4, so = ().

a、7 B、8 C、9 D、 10

4. One of the geometric series >; 0, and then = ()

a、5 B、6 C、 10 D、 18

5. In the process of culture, a bacterium divides every 20 minutes (1 divides into 2). After 3 hours, the bacteria can be isolated from 1: ()

a，5 1 1 b，5 12 c， 1023 d， 1024。

6. If the sum of the first three items of a arithmetic progression is 34, and the sum of the last three items is 146, the sum of all items.

Is 390, then this series has ()

A, projects 13 B, 12 C, 1 1 D and 10.

7, known as an increasing sequence, and for any constant, it is a real number.

The value range of is: ()

A, B, C, D,

Two. Filling (5 points× 4 = 20 points):

8. Sequence X, a 1, a2, a3, Y and X, b 1, b2, Y is arithmetic progression, x≠y, then

9. If the sum of the first 1 1 terms of arithmetic progression {an} is known as S 1 1=66, then a6=

10, geometric series {an}, an >；; 0, the common ratio Q 1, A5, A7 and A8 become arithmetic progression, then the common ratio q=

In 1 1 and geometric series {an}, if a5-a 1= 15 and a4-a2=6, then a3=

Three. Answer (***45 points):

12, there are four numbers, among which the first three numbers are arithmetic progression, the last three numbers are geometric progression, the sum of the first two numbers is 16, and the sum of the second two numbers is 12. Find these four numbers. (10)

13. In the known arithmetic progression, A 1 =-3, 1 1A5 = 5a8. Find the minimum value of the first n terms and Sn. (10)

14, known sequence {an}, sum of the first n terms Sn=2n-n2, an=log5bn, where bn >；; 0, find the sum of the first n terms of the sequence {bn}. (12)

15, the second item in arithmetic progression is 8, and the sum of the previous items 10 is 185.

(1) Find the general term formula of the sequence; (2) If the second item, the fourth item, the eighth item, ... and the first item, ... are taken out from the series, a series is formed in the original order, and the sum of the general term formula of the series and the first n items is found. (13)

Answer:

First, choose:

AACBB advertisement

Second, filling:

(8) (9)6 ( 10) ( 1 1) 4

Third, answer:

(1 2) 0,4,8, 16 or15,9,3,1

( 13)(Sn)min=S2=-4

( 14)an=3-2n，Sn=

( 15)①an = 3n+2；

②bn = 3×2n+2； Sn=3×2n+ 1+2n-6