Question

Identify the first 4 terms in the arithmetic sequence given by the explicit formula ƒ(n) = 8 + 3(n – 1).

A) 8, 11, 14, 17
B) 3, 11, 19, 27
C) 8, 5, 2, –1
D) 3, –5, –13, –21

Answer 1

A

Explanation:

an arithmetic sequence adds a constant from every previous term to create the next term.

it starts with a first term, a1, meaning that n >=1

a1 = 8 + 3×(1-1) = 8 + 3×0 = 8

so, B and D are out.

the next term is a2.

a2 = 8 + 3×(2-1) = 8 + 3×1 = 11

and so, only A can be correct.

just to verify

a3 = 8 + 3×(3-1) = 14

a4 = 8 + 3×(4-1) = 17

and it also fits overall,

starting with 8, every new term is the previous term + 3.