Question

What is the explicit formula for this geometric sequence?

-6, -18, -54, -162, ...
O A. 2,=-6(-3) (n = 1)
O B. a, = 3(-6)(n = 1)
O c. a = -6(3) -1)
O D. a = 6(3) -1)

Answer 1

(-6)×3ⁿ⁻¹

Explanation:

We notice that in this sequence (an) we multiply by 3 each time to get the next term

e.g : (-6)×3 = -18

then

the commonn ratio q = 3

the first term a1 = -6

the explicit formula :

an = a1×qⁿ⁻¹ = (-6)×3ⁿ⁻¹