Question

Which formula can be used to describe the sequence? –81, 108, –144, 192, ...

Answer 1

Answer:

a(n) = -81(-4/3)^(n - 1)

Step-by-step explanation:

The first term is -81.  From -81 we obtain the next term, 108, by multiplying -81 by -4/3.  Note how (-4/3)(108) = -144 as anticipated.

Thus, the common ratio is -4/3.

The explicit function for this geometric series is

a(n) = -81(-4/3)^(n - 1)