Answer:
[tex]\large\boxed{a_n=11-4n}[/tex]
Step-by-step explanation:
It's an arithmetic sequence.
The explicit formula of an arithmetic sequence:
[tex]a_n=a_1+(n-1)d[/tex]
We have
[tex]a_n=\left\{\begin{array}{ccc}a_1=7\\a_n=a_{n-1}-4\end{array}\right[/tex]
Therefore d = -4.
Substitute:
[tex]a_n=7+(n-1)(-4)[/tex] use distributive property
[tex]a_n=7-4n+4\\\\a_n=(7+4)-4n\\\\a_n=11-4n[/tex]
