Answer:
see explanation
Step-by-step explanation:
There is a common difference d between consecutive terms in the sequence, that is
9 - 5 = 5 - 1 = 1 - (- 3) = 4
This indicates the sequence is arithmetic with n th term
[tex]a_{n}[/tex] = a₁ + (n - 1)d
where a₁ is the first term and d the common difference
Here a₁ = - 3 and d = 4, thus
[tex]a_{n}[/tex] = - 3 + 4(n - 1) = - 3 + 4n - 4 = 4n - 7 ← explicit formula
Thus
[tex]a_{80}[/tex] = 4(80) - 7 = 320 - 7 = 313
