If three numbers A-4, a + 2 and 26-2a are properly arranged to form an increasing arithmetic sequence, find a and the corresponding sequence Why average

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• 1. The sum of the first n terms of the arithmetic sequence is 30, and the sum of the first 2n terms is 100?
• 2. If the sum of the first n terms of an arithmetic sequence is 48 and the sum of the first 2n terms is 60, then the sum of the first 3N terms of an arithmetic sequence is 48 Is it 72?
• 3. It is known that {an} is an arithmetic sequence, A1 = 2, A2 = 3. If three numbers are inserted between every two adjacent terms to form a new arithmetic sequence with the number of the original sequence, we can find: (1) what is the 12th term of the original sequence? (2) What is the 29th item of the new sequence?
• 4. It is known that the sequence {an} is an arithmetic sequence, A1 = 2, a7 = 11. If five numbers are inserted between every two terms, they will form a new arithmetic sequence with the number of the original sequence What is the 65th term of the new sequence?
• 5. The ratio of the sum of the first n terms of two arithmetic sequences is 2n / (3N + 1), and the ratio of the nth term of two arithmetic sequences is calculated
• 6. The sum of the first n items of the arithmetic sequence is a, the sum from the N + 1 to the 2n items is B, and the sum from the 2n + 1 to the 3N items is C. (1) the known tolerance is D, and D is b-a (2) Prove that a, B and C are equal difference sequence
• 7. Given that f (x) satisfies f (x + y ^ 2) = f (x) + 2 (f (y)) ^ 2 for any natural number x and y, and f (1) is not equal to 0, then f (2012) =?
• 8. When n is a positive integer, the function n & nbsp; (n) is defined to represent the largest odd factor of N. for example, n & nbsp; (3) = 3, n & nbsp; (10) = 5 Let s (n) = n (1) + n (2) + n (3) + +Then (1) s (4) = n (2n)___ ．（2）S（n）= ___ ．
• 9. The function f (x) whose domain is n + and whose value is also a positive integer: for any n ∈ n +, f (n + 1) > F (n); f (f (n)) = 3N, find f (4), f (5) We know that {f (n)} is a strictly increasing positive integer sequence -- > F (n) ≥ n f(f(1))=3≤f(3)--->f(1)≤3 If f (1) = 1, it is contradictory to f (1)) = 3; if f (1) = 3 --- > F (1)) = f (3) = 3, it is contradictory So: -- > F (1) = 2, f (2) = f (f (1)) = f (2) = 3 f(3)=f(f(2))=6 f(6)=f(f(3))=9 Because {f (n)} is a strictly increasing positive integer sequence -->f(4)=7,f(5)=8 How did you get this step? f(6)=f(f(3))=9 Because {f (n)} is a strictly increasing positive integer sequence
• 10. If the function f (x) = (m-2) x multiplied by X + (m-1) x + 2 is even, find the monotone decreasing interval of F (x + 1) and explain the reason
• 11. Sequence 23,27,26,8,29,1,32, ()
• 12. If there are 3N items in the equal ratio sequence {an}, the sum of the first 2n items is 100 and the sum of the last 2n items is 200, then how much is the sum of the middle n items in the equal ratio sequence
• 13. A is a natural number greater than 0. When a (), a of 5 is a true fraction
• 14. If x of 9 is a true fraction and X of 7 is a false fraction, then x is a natural number=
• 15. The object is subjected to three forces, two of which are 5N and 7n respectively. The maximum value of the resultant force of these three forces is 21n, then the size of the third force is 5N______ N. The minimum of the resultant of the three forces______ N．
• 16. In the equation 3x = 10 + a about X, a is a negative integer, and the solution of this equation is a natural number. Try to find the value of a and the solution of this equation
• 17. The two adjacent natural numbers (except 0) of the judgment question (1) must be prime numbers. (2) two different prime numbers must be coprime numbers. (3) two kinds of numbers that become coprime numbers. At least one number is prime
• 18. What is a prime number? Is it the same as a prime number? And is 0 a natural number? I've been working on the topic these days
• 19. According to the natural number from small to large as the standard order, find the following permutation of reverse order number 25 （3n-1）3 6… （3(n-1））（3n)
• 20. If inequality 1 / (n + 1) + 1 / (n + 2) + +If 1 / (n + 2n) > m / 2100 holds for all natural numbers n greater than 1, then the maximum value of integer m is