Chapter 5 - Number Theory and the Real Number System - 5.7 Arithmetic and Geometric Sequences - Exercise Set 5.7 - Page 329: 9

$a_1=7\\ a_2=4\\ a_3=1\\ a_4=-2\\ a_5=-5\\ a_6=-8$

In an arithmetic sequence, the next term can be found by adding the common difference $d$ to the previous term. Thus, with $a_1=7$ and $d=-3$, the first six terms are: $a_1=7\\ a_2=7+(-3)=4\\ a_3=4+(-3)=1\\ a_4=1+(-3)=-2\\ a_5=-2+(-3)=-5\\ a_6=-5+(-3)=-8$