Question

Write an explicate formula for this sequence -2, 6, -18, 54

Answer 1

`a_(n)` = - 2
`(-3)^(n-1)`

Explanation:

There is a common ratio r between consecutive terms, that is

r = 6 ÷ - 2 = - 18 ÷ 6 = 54 ÷ - 18 = - 3

This indicates the sequence is geometric with explicit formula

`a_(n)` = a₁
`(r)^(n-1)`

where a₁ is the first term and r the common ratio

Here a₁ = - 2 and r = - 3 , then

`a_(n)` = - 2
`(-3)^(n-1)`

Answer 2

7 =121 and t underscore 15 =193

Explanation: