arithmetic sequence/series?

Question

Use the following information to construct the arithmetic series, indicate the first term, common difference, and value of the iPhone after 3 years with an initial cost of $200 and a depreciation of $30 each year.

Answer 1

 

This scenario can be represented as an arithmetic sequence

 

The base formula is

 

     a_n = a₁ + (n -  1)d

 

         where

              a₁ = first term

              d = common difference

              n = the term number

 

The first term (a₁)+ = 200

The common difference (d) = - 30, because it depreciates by this amount each year

 

      a = 200 + (n - 1)(-30)

         = 200 -30n + 30

         = 230 -30n

 

     a_n = 230 - 30n