Question

If the sum of first n terms of a series be 5n^2+2n,then 2nd term=?

Answer 1

Arithmetic series ?

Answer 2

it says n terms so i guess yes

Answer 3

S2 - S1 = T2

Answer 4

ive forgot how to solve these type of questions,long time..

Answer 5

Can u Solve nw @DLS

Answer 6

no

Answer 7

By putting n=1 you will get first term, \(S_1\)

By n =2 you will get Sum of First two terms : \(S_2\)

For Second Term:

\[T_2 = S_2 - S_1\]

Answer 8

another method.(longer)
Sn = n/2(2a+(n-1)d) = n/2(10n+4)
so, 2a-d = 4
nd=10n---->d=10
2a = 14---->a=7
T2= 7+d=17

Answer 9

If your series is arithmetic, then subtract \(S_1\) from \(S_2\) because \(S_1\) is the first term.

Answer 10

It is Arithmetic Series..

Answer 11

one obvious way is as @Yahoo! said,,
other long method might be to find what series adds up to this..i.e.
we have 5n^2 + 2n
=> 5(n^2 + n) - 3n
=>10n(n+1)/2 - 3n

this represents
summation(10n - 3)

i.e. nth term = 10n-3

so 2nd term = 10*2 -3 = 17
voila! :D

Answer 12

Let me explain. Take \(k_1\) to be the first term and \(k_2\) the second. You are doing something like this:\[S_2 - S_1 = k_1 + k_2 - k_1 = k_2\]

Answer 13

so many methods!

Answer 14

@hartnn @shubhamsrg what is "a" in sn=n/2(2a+(n-1)d)?

Answer 15

a= 1st term

Answer 16

@ParthKohli yes it is..

Answer 17

i mean what is the value of a:/

Answer 18

\(a\) is the first term.

Answer 19

and the value of a =?

Answer 20

Put n = 1 there you will get a..

Answer 21

okay

Answer 22

As I told you earlier, \(S_1 = T_1 = a\).

Answer 23

okay,thhanks!

Answer 24

You're welcome =)