The sum of the first nine items of the arithmetic sequence with Prime Minister 25 is equal to the sum of the first 17 items. How many items of the arithmetic sequence have the largest sum?

The sum of the first nine items of the arithmetic sequence with Prime Minister 25 is equal to the sum of the first 17 items. How many items of the arithmetic sequence have the largest sum?

∵S9=S17
∴8a1=9a9-17a17 ①
a9=a1+8d ②
a17=a1+16d ③
A1 = 25, three simultaneous, solution: D = - 2
So, an = - 2n + 27
Let an ≥ 0, the solution is n ≤ 13.5
So the sum of the first 13 items is the largest

The sum of the first 9 items of an arithmetic sequence with the first 25 is equal to the sum of the first 17 items

The first term is a positive number, so the tolerance is d0
a14=d/2

What does the rabbit sequence mean

In mathematics, Fibonacci sequence is defined recursively as follows: F0 = 0, F1 = 1, FN = f (n-1) + F (n-2) (n > = 2, n ∈ n *)