Question:
If the sum of $n$ terms of an $A P$ is given by $S_{n}=\left(2 n^{2}+3 n\right)$, then find its common difference.
Solution:
Given: $S_{n}=\left(2 n^{2}+3 n\right)$
To find: find common difference
To find: find common difference
Put $n=1$ we get
$S_{1}=5$ OR we can write
$a=5 \ldots$ equation 1
Similarly put $\mathrm{n}=2$ we get
$\mathrm{S}_{2}=14 \mathrm{OR}$ we can write
$2 a+d=14$
Using equation 1 we get
d = 4
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