Answer
First three terms : $4,8,12$ ; Last Term :$400$ and Sum $20200$
Work Step by Step
Here, $a_n=4i$
Plug $i=1,2,3$, in the given equation.
Then we have the first three terms are: $4,8,12$
Last term : $a_{100}=400$
The sum of an arithmetic sequence is given by: $S_n=\dfrac{n}{2}[a_1+a_n]$
or, $S_{100}=\dfrac{100}{2}[4+400]=20200$
Hence, First three terms : $4,8,12$ ; Last Term :$400$ and Sum $20200$
