Answer
First three terms : $-4,-8,-12$ ; Last Term :$-200$ and Sum $-5100$
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 : $a_{50}=-200$
The sum of an arithmetic sequence is given by: $S_n=\dfrac{n}{2}[a_1+a_n]$
or, $S_{50}=\dfrac{50}{2}[4-200]=-5100$
Hence, First three terms : $-4,-8,-12$ ; Last Term :$-200$ and Sum $-5100$
