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

Vedclass pdf generator app on play store
Vedclass iOS app on app store
(10N-8) Given the sum of $n$ terms: $S_{n} = 5n^{2} - 3n$.
We know that the $n^{th}$ term $T_{n}$ is given by $T_{n} = S_{n} - S_{n-1}$ for $n > 1$.
First,find $S_{n-1}$:
$S_{n-1} = 5(n-1)^{2} - 3(n-1)$
$S_{n-1} = 5(n^{2} - 2n + 1) - 3n + 3$
$S_{n-1} = 5n^{2} - 10n + 5 - 3n + 3$
$S_{n-1} = 5n^{2} - 13n + 8$.
Now,calculate $T_{n}$:
$T_{n} = (5n^{2} - 3n) - (5n^{2} - 13n + 8)$
$T_{n} = 5n^{2} - 3n - 5n^{2} + 13n - 8$
$T_{n} = 10n - 8$.
For $n = 1$,$T_{1} = S_{1} = 5(1)^{2} - 3(1) = 2$.
Using the formula $T_{n} = 10n - 8$,for $n = 1$,$T_{1} = 10(1) - 8 = 2$.
Since both match,the $n^{th}$ term is $T_{n} = 10n - 8$.

Explore More

Similar Questions

Find the number of terms in the following $AP$: $18, 15 \frac{1}{2}, 13, \ldots, -47$.

Find the $100^{th}$ term of the $A.P.$ $50, 56, 62, 68, \ldots$

To clear a debt,Ajaybhai has to pay $Rs. 100$ in the first monthly instalment,$Rs. 150$ in the second monthly instalment,and onwards he has to pay in each monthly instalment $Rs. 50$ more than what was paid in the previous instalment. He has to pay $24$ monthly instalments in all. What amount will he pay in the $24^{th}$ instalment?

Difficult
View Solution

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

The $n^{th}$ term of an $A.P.$ is given by $T_n = 3n - 1$. For this $A.P.$,the common difference $d = \ldots$

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