Answer
$$\eqalign{
& {a_n} = - 20n + 30 \cr
& {\text{The domain is }}D:\left\{ {1,2,3,4,5} \right\} \cr
& {\text{The range is }}R:\left\{ { - 70, - 50, - 30, - 10,10} \right\} \cr} $$
Work Step by Step
$$\eqalign{
& {\text{From the graph we can see that}} \cr
& {a_1} = 10{\text{ and }}{a_2} = - 10 \cr
& {\text{Find }}d \cr
& d = {a_{n + 1}} - {a_n} \cr
& d = - 10 - 10 \cr
& d = - 20 \cr
& \cr
& {\text{The }}n{\text{th Term of an Arithmetic Sequence is given by}} \cr
& {a_n} = {a_1} + \left( {n - 1} \right)d \cr
& {\text{Then}} \cr
& {a_n} = 10 + \left( {n - 1} \right)\left( { - 20} \right) \cr
& {a_n} = 10 - 20n + 20 \cr
& {a_n} = - 20n + 30 \cr
& {\text{The domain is }}D:\left\{ {1,2,3,4,5} \right\} \cr
& {\text{The range is }}R:\left\{ { - 70, - 50, - 30, - 10,10} \right\} \cr} $$
