The recursive formula, a1 = 18.5, an = an−1 + 1.5 models the number of people, in millions, that
own a smartphone in the U.S. n years after 2014. Write an equivalent explicit formula for the
situation.
+208 http://mrswisey.weebly.com/uploads/2/3/3/9/23393696/d3-_arithmetic_sequences_answer_key_all.pdf
scroll down to question 10 (I think it's the same question)
