## Functions Modeling Change: A Preparation for Calculus, 5th Edition

In order for a sequence to be arithmetic, the difference of all consecutive terms must be constant. Here: $a_2-a_1=7-2=5$ $a_3-a_2=12-7=5$ $a_4-a_3=17-12=5$ Thus we can see that the difference is constant, thus it is an arithmetic sequence.