Answer:
see explanation
Step-by-step explanation:
The explicit formula for an arithmetic sequence is
[tex]a_{n}[/tex] = a₁ + (n - 1)d
where a₁ is the first term and d the common difference
Here a₁ = 11 and d = a₂ - a₁ = 1 - 11 = - 10 , then
[tex]a_{n}[/tex] = 11 - 10(n - 1) = 11 - 10n + 10 = 21 - 10n ← explicit formula
Using the explicit formula to find a₄₀ , then
a₄₀ = 21 - 10(40) = 21 - 400 = - 379
