In the arithmetic sequence {an}, A1 = 25, S9 = S17, then______ Item and maximum
∵ A1 = 25, S9 = S17, ∵ 9a1 + 9 × 82d = 17a1 + 17 × 162d, the solution is d = - 2. ∵ Sn = 25N + × n (n − 1) 2 (- 2) = - N2 + 26n = - (N-13) 2 + 169
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- 1. In the arithmetic sequence {an}, A1 = 25, S17 = S9, find the general term formula of {an} (important process)
- 2. We know the arithmetic sequence {an} A1 = 25, S17 = S9; The known arithmetic sequence {an} A1 = 25, S17 = S9 \X05 (1) the general formula of {an}; \x05(2)S1、S2、… Which one is the largest? And find the maximum
- 3. If the general term formula of sequence {an} is an = n ^ 2cosn π and Sn is the sum of its first n terms, then (s2012) / 2013 is obtained Hurry up. It's urgent
- 4. If the general term formula of sequence an is an = ncosn π / 2 + 1 and the sum of the first n terms is Sn, then s2012 =
- 5. The general term formula of sequence {an} is an = ncosn π 2 + 1, the sum of the first n terms is Sn, then s2012=______ .
- 6. Let the first n terms of sequence {an} and Sn = N2, then A8=______ .
- 7. The general term of sequence {an} is an = n & # 178; (COS & # 178; n π / 3-sin & # 178; n π / 3), and the sum of the first n terms is SN (1) Find SN; (2) Let BN = s (3n) / (n · 4N), find the first n terms and TN of the sequence {BN}
- 8. If the general term of sequence {a n} a n = n & # 178; (COS & # 178; n π / 3-sin & # 178; n π / 3), the sum of the first n terms is Sn, then S30 is?
- 9. If the general term an of sequence {an} is n ^ 2 {cos ^ (n * 180) / 3-sin ^ (n * 180) / 3}, and the sum of the first n terms is Sn, then S30 is?
- 10. If the sum of the first n terms of the sequence an is Sn, then S30 =?
- 11. In the arithmetic sequence {an}, A1 = 25, S9 = S17, then______ Item and maximum
- 12. In the arithmetic sequence {an}, A1 = 22, S17 = S9, find the maximum value of Sn
- 13. In the arithmetic sequence {an}, it is known that A1 > 0, Sn is the sum of the first n terms of the sequence, if S9 > 0, S10
- 14. In the arithmetic sequence, when A1 is greater than 0.s9 = S17 and N is equal to, Sn has the maximum value/
- 15. In the arithmetic sequence {an}, Sn is the sum of the first n terms of {an}, A1 = 25, S17 = S9, find the maximum value of Sn
- 16. In the arithmetic sequence {an}, if A1 < 0, S9 = S12, then n is equal to___ The minimum value of Sn is obtained
- 17. Given that the first term of the arithmetic sequence A1 = 25, and S9 = S17, ask what is the value of N, and what is the maximum value of Sn?
- 18. In known sequence an, A1 = 2, the first n terms and Sn, if Sn = n ^ 2An, find an
- 19. It is known that the sum of the first n terms of the sequence {an} is Sn and satisfies Sn = 2an-n, (n ∈ n *) (1) find the general term formula of the sequence {an}; (2) if BN = (2n + 1) an + 2n + 1 and the sum of the first n terms of the sequence {BN} is TN, find the minimum n value satisfying the inequality tn-22n-1 ≥ 128
- 20. Let the first n terms of the sequence {an} and Sn = 2an-2 ^ n 1. Find A3, A4; 2. Prove that: {an + 1-2an} is an equal ratio sequence 3. Find the general formula of {an} [sequence problem] I hope you will give generously and have a detailed process Thank you ~ o (≥ V ≤) O~~