Answer:
see explanation
Step-by-step explanation:
The terms form a geometric sequence with n th term
[tex]a_{n}[/tex] = a [tex](r)^{n-1}[/tex]
where a is the first term and r the common ratio
r = [tex]\frac{a_{2} }{a_{1} }[/tex] = [tex]\frac{a_{3} }{a_{2} }[/tex] = ......
r = [tex]\frac{-6}{3}[/tex] = [tex]\frac{12}{-6}[/tex] = - 2 and a = 3, hence
[tex]a_{n}[/tex] = 3 [tex](-2)^{n-1}[/tex] ← explicit formula
