Chapter 12 - Sequences; Induction; the Binomial Theorem - 12.2 Arithmetic Sequences - 12.2 Assess Your Understanding - Page 814: 8

In order for a sequence to be arithmetic, the difference of all consecutive terms must be constant. Hence here: $a_{n+1}-a_n=((n+1)-5)-(n-5)=(n-4)-(n-5)=1$, thus it is an arithmetic sequence. $a_1=-4$ $a_2=-3$ $a_3=-2$ $a_4=-1$

In order for a sequence to be arithmetic, the difference of all consecutive terms must be constant. Hence here: $a_{n+1}-a_n=((n+1)-5)-(n-5)=(n-4)-(n-5)=1$, thus it is an arithmetic sequence. $a_1=1-5=-4$ $a_2=2-5=-3$ $a_3=3-5=-2$ $a_4=4-5=-1$