The sum of the first $n$ terms of an $A.P.$ is given by $S_{n} = 3n^{2} + 5n$. Find the $n^{th}$ term of the $A.P.$

Vedclass pdf generator app on play store
Vedclass iOS app on app store
(N/A) The $n^{th}$ term of an $A.P.$ is given by the formula $a_{n} = S_{n} - S_{n-1}$ for $n > 1$.
Given $S_{n} = 3n^{2} + 5n$.
Then $S_{n-1} = 3(n-1)^{2} + 5(n-1) = 3(n^{2} - 2n + 1) + 5n - 5 = 3n^{2} - 6n + 3 + 5n - 5 = 3n^{2} - n - 2$.
Now,$a_{n} = (3n^{2} + 5n) - (3n^{2} - n - 2) = 3n^{2} + 5n - 3n^{2} + n + 2 = 6n + 2$.
For $n = 1$,$a_{1} = S_{1} = 3(1)^{2} + 5(1) = 8$.
Thus,the $n^{th}$ term is $a_{n} = 6n + 2$ for $n \geq 1$.

Explore More

Similar Questions

Yasmeen saves $Rs.\, 32$ during the first month,$Rs.\, 36$ in the second month,and $Rs.\, 40$ in the third month. If she continues to save in this manner,in how many months will she save $Rs.\, 2000$?

Difficult
View Solution

For the finite $A.P.$ $40, 35, 30, \ldots, -200,$ find the $10^{th}$ term from the end.

$3+6+9+12+\ldots+300 = \ldots$

For a given $A.P.$,the first term is $5$ and the common difference is $3$. Then the $15^{th}$ term of the $A.P.$ is.........

Find the sum of the first seven numbers which are multiples of $2$ as well as of $9$.

Vedclass Products

For Students

Vedclass Test Series

Mock tests in real JEE/NEET style with performance analysis. 5-day free trial.

Start Free Trial
For Teachers

Exam Paper Generator

Generate Set A/B/C/D exam papers from 7.5L+ questions in 2 minutes. 3 chapters free.

Try Free
For Institutes

Online Exam Module

Live online exams with unlimited students, 360° analytics & white-label branding.

See Demo