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

The correct option is 4.

Step-by-step explanation:

The given geometric sequence is

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

Here the first term of the sequence is 1 and the common ratio is

The explicit formula of a geometric sequence is

In the given geometric sequence a=1 and r=-3.

Substitute a=1 and r=-3 in the above formula.

The explicit formula of given geometric sequence is .

Therefore the correct option is 4.

not sure but it may be b, as i said i'm not sure.