Answer:
4th option
Step-by-step explanation:
The nth term of a geometric sequence is
[tex]a_{n}[/tex] = a₁ [tex](r)^{n-1}[/tex]
where a₁ is the first term and r the common ratio
To find a₁ use a₁₂ = - 12288 , then
a₁ [tex](2)^{11}[/tex] = - 12288 , that is
a₁ × 2048 = - 12288 ( divide both sides by 2048 )
a₁ = - 6
Then the explicit formula is
[tex]a_{n}[/tex] = - 6 . [tex]2^{n-1}[/tex]
