Question

Find an equation for the nth term of the sequence.

-1, -4, -16, -64, ...

an = -1 • 4n - 1
an = -1 • 4n
an = 4 • -1n
an = 4 • -1n + 1

Answer 1

Explanation:

Step 1: Find the sequence

Option A

`a(-1) = -1*4(-1)-1`

`a(-1) = -1 * -4 - 1`

`a(-1) = 4 - 1`

`a(-1) = 3`

Option B

`a(-1) = -1 * 4(-1)`

`a(-1) = -1 * -4`

`a(-1) = 4`

Option C

`a(-1) = 4 * -1(-1)`

`a(-1) = 4 * 1`

`a(-1) = 4`

Option E

`a(-1) = 4 * -1(-1) + 1`

`a(-1) = 4 * 1 + 1`

`a(-1) = 4 + 1`

`a(-1) = 5`

Answer: For some reason, none of the answer choices match

Answer 2

First one

Explanation:

It is a Geometric sequence with:

first term: -1

common ratio: -4/-1 = 4

Nth term: a × r^(n-1)

-1 × 4^(n-1)