Answer:
[tex]a_{n}[/tex] = 90 - 3n
Step-by-step explanation:
There is a common difference between consecutive terms, that is
84 - 87 = 81 - 84 = - 3
This indicates the sequence is arithmetic with nth term
[tex]a_{n}[/tex] = a₁ + (n - 1)d
where a₁ is the first term and d the common difference
Here a₁ = 87 and d = - 3 , then
[tex]a_{n}[/tex] = 87 - 3(n - 1) = 87 - 3n + 3 = 90 - 3n
