Question

H e l p m e h pls

What is the formula for the following arithmetic sequence? -9, -2, 5, 12, ...
a) an = -9 + 7( n - 1)
b) an = -9 + (-7)( n - 1)
c) an = 7 + (-9)( n - 1)
d) an = 9 + (-7)( n - 1)

Answer 1

a(n) = -9 + 7(n - 1) (Answer a)

Explanation:

Each new term is found by adding 7 to the previous term. Thus, the formula will include "+ 7." The first term is -9.

The general formula for an arithmetic sequence is a(n) = a(1) = h(n - 1), where h is the "common difference" (which here is 7).

Thus, the desired formula is a(n) = -9 + 7(n - 1) (Answer a)