Only answer if your 100% sure what equation is shown in the graph?

(0,2) and (1,1)
slope = (2 - 1)/(0 -1) = -1
y intercept b = 2
equation
y = -x + 2

answer
equation
y = -x + 2

 In any arithmetic sequence, each term is equal to the previous term plus the common difference. 

 Thus, the second term is equal to the first term plus the common difference. In this sequence, the second term, 5, is 3 less than the first term, 8. 

 Therefore, the common difference is -3.