A)
1) Let's insert the Recursive formula for a:
[tex]\begin{gathered} a_n=a_{n-1}+4 \\ a_1=-3 \\ f(n)=-3\text{ +(n-1)4} \\ f(n)=-3\text{ +4n-4} \\ f(n)=4n-7 \end{gathered}[/tex]When we apply the General formula f(n) we'll need the first term. for that sequence, and then rearrange it we find the function for the nth term of that Arithmetic Sequence.
All we need now is to plug into the formula the nth term we want to find out.