Let `a_1,a_2,a_3,...` be in harmonic progression with `a_1=5a n da_(20)=25.` The least positive integer `n` for which `a_n<0` `22` b. `23` c. `24` d. `25`

If a_1,a_2,a_3 …. are in harmonic progression with a_1=5 and a_20=25 . Then , the least positive integer n for which a_n lt 0 , is :

let a_1,a_2,a_3........be an arithmetic progression with comman difference 2. let S_n be the sum of first n terms of the sequence . if S_(3n)/s_n does not depend on n then the sim of the first 10 terms.

Let a_n be the n^(th) term of an arithmetic progression. Let S_(n) be the sum of the first n terms of the arithmetic progression with a_1=1 and a_3=3_(a_8) . Find the largest possible value of S_n .

If a_1,a_2,a_3,…….a_n are in Arithmetic Progression, whose common difference is an integer such that a_1=1,a_n=300 and n in[15,50] then (S_(n-4),a_(n-4)) is

"If "a_1,a_2,a_3,.....,a_n" are in AP, prove that "a_(1)+a_(n)=a_(r)+a_(n-r+1)""

If a_1,a_2,a_3,....a_n and b_1,b_2,b_3,....b_n are two arithematic progression with common difference of 2nd is two more than that of first and b_(100)=a_(70),a_(100)=-399,a_(40)=-159 then the value of b_1 is

Let a_1,a_2,a_3 ......, a_n are in A.P. such that a_n = 100 , a_40-a_39=3/5 then 15^(th) term of A.P. from end is

Let a_1,a_2,a_3…………., a_n be positive numbers in G.P. For each n let A_n, G_n, H_n be respectively the arithmetic mean geometric mean and harmonic mean of a_1,a_2,……..,a_n On the basis of above information answer the following question: A_k,G_k,H_k are in (A) A.P. (B) G.P. (C) H.P. (D) none of these