I have a recursive sequence and need to answer with a function

Question

$a_n=a_{n-1}+4$, $a_1=-3$

What function can I use to determine the nth term?

Answer 1

$a_n-a_{n-1}=4$ $\Rightarrow$ $a_{x+n}=a_x+4((n+x)-x)$

$a_{x+n}=a_x+4n$ $\Rightarrow$ $a_n=a_0+4n$