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` a.`22` b. `23` c. `24` d. `25`

Let a_(1),a_(2),a_(3), . . . be a harmonic progression with a_(1)=5anda_(20)=25 . The least positive integer n for which a_(n)lt0 , is

Let a_1, a_2, a_3, ,a_(100) be an arithmetic progression with a_1=3a n ds_p=sum_(i=1)^p a_i ,1lt=plt=100. For any integer n with 1lt=nlt=20 , let m=5ndot If (S_m)/(S_n) does not depend on n , then a_2 is__________.

Let a_1,a_2,a_3…… ,a_n be in G.P such that 3a_1+7a_2 +3a_3-4a_5=0 Then common ratio of G.P can be

If a_1,a_2,……….,a_n are in H.P. then expression a1a2+a2a3+......+a_n-1an

cIf a_1,a_2,a_3,..,a_n in R then (x-a_1)^2+(x-a_2)^2+....+(x-a_n)^2 assumes its least value at x=

Let A_1 , A_2 …..,A_3 be n arithmetic means between a and b. Then the common difference of the AP is

Let a_1, a_2, a_3, ....a_n,......... be in A.P. If a_3 + a_7 + a_11 + a_15 = 72, then the sum of itsfirst 17 terms is equal to :

Let a_1,a_2,a_3..... be an arithmetic progression and b_1,b_2,b_3...... be a geometric progression. The sequence c_1,c_2,c_3,.... is such that c_n=a_n+b_n AA n in N. Suppose c_1=1.c_2=4.c_3=15 and c_4=2. The common ratio of geometric progression is equal to "(a) -2 (b) -3 (c) 2 (d) 3 "

Let a_1, a_2, a_3, ,a_(101) are in G.P. with a_(101)=25a n dsum_(i=1)^(201)a_1=625. Then the value of sum_(i=1)^(201)1/(a_1) equals____________.

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