Answer:
; all integers where n ≥ 1
Step-by-step explanation:
We are given that the first term of the sequence is 4 i.e.
and second term is -12 i.e.
.
Now, the nth term of geometric sequence is given by,
, where r is the common ratio of the sequence.
So, using the given values we get,

i.e. 
i.e. 
i.e. r = -3.
Now the explicit formula for the geometric equation is given by,
.
i.e.
, where 
Hence option first is correct.