Question

One year after Sarah started a new job, she had $1200 in her savings account. Each year, she added $900 more to the savings account.

What function, written in sequence notation, models Sarah’s savings account balance n years after starting her new job?



A. an=300n+900

B. an=900n+300

C. an=300n+1200

D. an=900n+1200

Answer 1

The formular for a sequence with first term, a, and increases at a rate of d is given by:


`a_n=a+(n-1)d`

Here: a = 1200, d = 900

Thus,


`a_n=1200+900(n-1) \\ \\ =1200+900n-90=300+900n`

Therefore, the function, written in sequence notation, which models Sarah’s savings account balance n years after starting her new job is an = 300 + 900n