Consider a sequence whose sum of first n -terms is given by Sₙ = 4n^2 + 6n, n ∈ N , t

English

Gujarati

Hindi

8. Sequences and Series

medium

Consider a sequence whose sum of first $n$ -terms is given by $S_n = 4n^2 + 6n, n \in N$, then $T_{15}$ of this sequence is -

A

$118$

B

$120$

C

$122$

D

$86$

Solution

$T_n = S_n -S_{n-1}$
$\Rightarrow T_n = (4n^2 + 6n) -(4(n -1)^2 + 6(n-1))$
$T_n = 8n + 2 \Rightarrow T_{15} = 122$

Standard 11

Mathematics

Share

Similar Questions

The $p^{\text {th }}, q^{\text {th }}$ and $r^{\text {th }}$ terms of an $A.P.$ are $a, b, c,$ respectively. Show that $(q-r) a+(r-p) b+(p-q) c=0$

hard

Let $S_n$ denote the sum of the first $n$ terms of an $A.P$.. If $S_4 = 16$ and $S_6 = -48$, then $S_{10}$ is equal to

hard

(JEE MAIN-2019)

The sum of integers from $1$ to $100$ that are divisible by $2$ or $5$ is

medium

(IIT-1984)

The sides of a right angled triangle are in arithmetic progression. If the triangle has area $24$ , then what is the length of its smallest side ?

medium

(IIT-2017)

Insert $6$ numbers between $3$ and $24$ such that the resulting sequence is an $A.P.$

medium