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It is known that the sum of the first n terms of the arithmetic sequence {an} is Sn, if A4 = - 12, a8 = - 4 Take A1, A2, A4, A8 a2^n-1…… To construct a new sequence {BN}, find the first n terms and TN of {BN}
d=(-4+12)/4=2a4=a1+3*2=-12,a1=-18an=-18+2(n-1)=2n-20b1=a1=-18b2=a2=-16b3=a4=-12b4=a8=-4…… bn=a[2^(n-1)]=2[2^(n-1)]-20=2^n-20 Tn=[2^n-20]+[2^(n-1)-20]+[2^(n-2)-20]+…… +[2^2-20]+[2^1-20]=[2^n+2^(n-1)+...
RELATED INFORMATIONS
- 1. If the sum of the first n terms in the arithmetic sequence (an) is Sn and S3 = 8 and S8 = 42 are known, then the value of A8 is A: 16 B: 18 C: 20 D: 22 is the question wrong?
- 2. If A1 = 4, a8 = 18, then S8 =? Do me a favor
- 3. If A1 = - 25 S3 = S8 in {an} is known, then the minimum value of the first n terms and Sn is? 2 LG (A1) + LG (A2) +... In the sequence {an} +LG (A10) = 5 and LG (а n + 1) - LG (an) = 1 Find an =?
- 4. It is known that SN is the sum of the first n terms of the equal ratio sequence {an}, S3, S9 and S3 are equal difference sequence, and A2, a8 and A5 are equal difference sequence It's a long story
- 5. Let Sn be the sum of the first n terms of the equal ratio sequence {an}, S3, S9 and S6 be equal difference sequence, and A2 + A5 = 2am, then M is equal to () A. 6B. 7C. 8D. 10
- 6. In the arithmetic sequence {an}, Sn is the sum of the first n terms, A2 + A8 = 18-a5, then S9=______ ．
- 7. In the plane rectangular coordinate system, the coordinate of point a is (3,0), and point B is a point on the positive half axis of X axis. Point C is a point in the first quadrant, and AC is 2. Let Tan angle BOC = m, then the value range of M is?
- 8. Finding the minimum value of the square of a + 2a-1
- 9. How many microns is a millimeter?
- 10. The square of 3 (x + y) - 7 (x + y) + 8 (x + y) + 6 (x + y) - 11 (x + y) =?
- 11. If we know that A3 = 2, a7 = 1 in {an} and that {an} is an arithmetic sequence, then A8 =?
- 12. The first n terms of the arithmetic sequence {an} and the maximum value of Sn are only S7, and | A7 | < | A8 |, then the maximum value of n with Sn > 0 is______ ．
- 13. In the arithmetic sequence {an}, Sn is the sum of the first n terms, and S7 is the largest, the largest positive integer n of | A7 | 0? There seem to be two answers, one is 12 and the other is 13-
- 14. Given that the sum of the first n terms of the arithmetic sequence {an} is Sn, and A3 + A8 = 13, S7 = 35, then A7=______ ．
- 15. The sum of the first n terms of the arithmetic sequence {an} is SN. It is known that S7 is the maximum value of Sn and the absolute value of A7 is less than the absolute value of A8. Find the maximum value of n with Sn greater than 0... Help, urgent
- 16. The sum of the first n terms of sequence an is Sn = n ∨, # 178; what is A8 equal to?
- 17. Given the first n terms of sequence {an} and Sn = N2 + 3N + 1, then the general term formula of sequence {an} is______ ．
- 18. If the first n terms of the sequence {an} and Sn = n2-10n (n = 1,2,3...), then the general term formula of the sequence is What is the smallest term in the sequence {Nan}
- 19. Given the first n terms of the sequence {an} and Sn = N2, we can find the general term formula of the sequence
- 20. If the first n terms of sequence {an} and Sn = N2 + 1, find the general term formula