Question

Look at the sequence given below.

4, 0, -4, -8, ...

If n = 1 represents the first term in the sequence above, which of the following describes the nth term of the sequence?

A. -3n + 4

B. n + 3

C. -4n + 8

D. -4n + 3

Answer 1

C. -4n + 8

Explanation:

Try the formulas and see which works.

__

The common difference is -4, so the coefficient of n in the explicit formula is -4. Every term is divisible by 4, so there won't be 3 anywhere in the formula.

__

-4·1 +8 = 4

-4·2 +8 = 0

-4·3 +8 = -4

-4·4 +8 = -8

The formula -4n+8 reproduces the sequence exactly.