In an A.P.,8, 11, 14, .......... find `S_(n) – S_(n – 1)`

S_n in A.P.=

If of an A.P. t_7 =13 , S_14=203 , find S_8 .

If in an A.P., S_(2n)=3.S_(n) then S_(3n) : S _(n) = (a)5 (b) 6 (c)7 (d)8

In an A.P, a=8 , t_n=62 , S_n=210 , then find n . a) 5 b) 6 c) 7 d) 8

In an A.P., if a = 1 , a_(n) = 20 and S_(n) = 399 , then n = ……..

In an A.P. find S_(n) where a_(n) = 5n-1 . Hence find the sum of the first 20 terms.

If S_(n) denotes the sum of n terms of an A.P., S_(n +3) - 3S_(n + 2) + 3S_(n + 1) - S_(n) =

In an A.P., S_(m) = n and S_(n) = m also m gt n ,find the sum of first (m-n) terms .

If S_(n) danotes the sum of n terms of n terms of an A.P. then S_(n + 3) - 3 S_(n + 2) + 3S_(n + 1) - S_(n) =

In an A.P., if a = 8,a_(4), = 17, S_(n) = 148 then value of n is.