Answer
First three terms : $4,2,0$ ; Last Term :$-74$ and Sum $-1400$
Work Step by Step
Here, $a_n=-2i+6$
Plug $i=1,2,3$, in the given equation.
Then we have the first three terms are: $4,2,0$
Last term : $a_{40}=-2(40)+6 =-74$
The sum of an arithmetic sequence is given by: $S_n=\dfrac{n}{2}[a_1+a_n]$
or, $S_{40}=\dfrac{40}{2}[4+(-74)]=-1400$
Hence, First three terms : $4,2,0$ ; Last Term :$-74$ and Sum $-1400$
