Question

Find the 9th term of 3 -15 75

Answer 1

a₉ = 1171875

Explanation:

There is a common ratio r between consecutive terms

r = - 15 ÷ 3 = 75 ÷ = 15 = - 5

This indicates the sequence is geometric with n th term

`a_(n)` = a₁
`r^(n-1)`

where a₁ is the first term and r the common ratio

Here a₁ = 3 and r = - 5, then

a₉ = 3 ×
`(-5)^(8)`

= 3 × 390625

= 1171875