Question

Write the sum of the first three terms of the following sequence whose $n^{th}$ term is $3n+1$.

Answer 1

Given, $T_n=3n+1$
So, $T_1=3+1=4$
$T_2=3\left(2\right)+1=7$
$T_3=3\left(3\right)+1=10$
Required $S_3=$ Sum of these $3$ terms $=4+7+10=21$