Question

For the following geometric sequence, find the explicit formula.

{1, -3, 9, ...}

an = -3 · an - 1 where a1 = 1
an = -3 · an - 1 where a1 = -1
an = -1 · (-3)n - 1
an = (-3)n - 1

Answer 1

Answer:
`a_(n) = (-3)^(n-1)`

Explanation:

`a_(n) = a_(1) r^(n-1)` ; where a₁ is the first term and r is the ratio

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

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