Question

What is the formula for the following geometric sequence?

Answer 1

Answer:

Correct answer:  Third answer  aₙ = -5 · 2⁽ⁿ ⁻ ¹⁾

Step-by-step explanation:

Given:

-5, -10, -20, -40,.....

First term       a₁ = -5

Second term a₂ = -10

Third term     a₃ = -20

Common ratio or quotient

q = a₂ / a₁ = a₃ / a₂ = -10 / -5 = -20 / -10 = 2

q = 2

First term  a₁

Second term a₂ = a₁ · q = a₂ · q²

Third term     a₃ = a₂ · q = a₁ · q³

.....................................................

n-th term aₙ = a₁ · q⁽ⁿ ⁻ ¹⁾

aₙ = -5 · 2⁽ⁿ ⁻ ¹⁾

God is with you!!!

Answer 2

Answer:

an = -5 · 2 n - 1

Hope it helped <3