Answer:
The explicit formula for a given geometric sequence is of the form

Explanation:
Given sequence is

Let
To find the common ratio r:



Therefore r=-3



Therefore r=-3
Therefore common ratio is -3
Therefore given sequence is geometric sequence.
The explicit formula for a geometric sequence is
, where common ratio is r.
From given sequence we are having r=-3
Therefore the explicit formula for a given geometric sequence is of the form


