Question

What is the 20th term of the linear sequence below?
15,7,-1,−9,−17

Answer 1

a₂₀ = - 137

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

`a_(n)` = 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