Answer:
= 13 - 4n
Explanation:
Note the common difference d between consecutive terms, that is
d = 5 - 9 = 1 - 5 = - 3 - 1 = - 7 - (- 3) = - 4
This indicates the sequence is arithmetic with n th term
= a₁ + (n - 1)d
where a₁ is the first term and d the common difference
Here a₁ = 9 and d = - 4, thus
= 9 - 4(n - 1) = 9 - 4n + 4 = 13 - 4n ← explicit equation