Question

If sum of n terms of an AP is $2n^2+5n,$ then its nth term is

• A. $4n+3$
• B. $4n+5$
• C. $4n+7$
• D. $4n+6$

Answer 1

Answer: (A)

Sum of n terms, $S_n=2n^2+5n$
$T_n=S_n-S_{n-1}$
$=2n^2+5n-[2{(n-1)}^2+5(n-1)]$
$=2n^2+5n-2n^2-2+4n-5n+5$
$=4n+3$