What is the recursive formula for this geometric sequence? 4, -12, 36, -108,

aₙ = 4(-1)ⁿ⁻¹(3)ⁿ⁻¹

Step-by-step explanation:

The formula for the nth term of a geometric sequence is

aₙ = a₁rⁿ⁻¹

We can get the value for r by dividing aₙ by aₙ₋₁.

a₄/a₃ = -108/36

a₄/a₃ = -3

      r = -3

    aₙ = 4(-3)ⁿ⁻¹

aₙ = 4(-1)ⁿ⁻¹(3)ⁿ⁻¹

The (-1)ⁿ⁻¹ term makes even-numbered terms negative.

$54.99

step-by-step explanation:

$54.99 includes 500 min. if she does not exceed 500 min then her bill is $54.99