Answer:
a₂₀ = - 137
Step-by-step explanation:
there is a common difference between consecutive terms , that is
7 - 15 = - 9 - (- 1) = - 17 - (- 9) = - 8
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 = 15 and d = - 8 , then
a₂₀ = 15 + (19 × - 8) = 15 + (- 152) = 15 - 152 = - 137
