Answer:
the third option
Step-by-step explanation:
a1 = 3
a2 = -9
as a geometric sequence every sequence item is created by multiplying a constant factor with the previous item.
what do I need to multiply 3 with to get -9 ? right, -3.
so, the first 2 options are out, because they multiply with -12.
and we can accept only n>=1, because there is no a0. it starts with a1.
ah only the third option is right.
