Answer
See below
Work Step by Step
Let's check the type of the quotients
$$\frac{a_2}{a_1}=\frac{12}{-4}=-3\\\frac{a_3}{a_2}=-\frac{36}{12}=-3\\\frac{a_4}{a_3}=\frac{108}{-36}=-3$$
We can see that the quotients are constant, so the sequence has a common ratio. Hence, the sequence is geometric.
The rule is: $$a_n=a_1\times r^{n-1}\\a_n=-4(-3)^{n-1}$$
The 8th term of this sequence is: $a_8=a_1\times r^{8-1}\\a_8=-4(-3)^7\\a_8=8748$
