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

In order for a sequence to be arithmetic, the difference of all consecutive terms must be constant. Hence here: $a_{n+1}-a_n=(4-2(n+1))-(4-2n)=(2-2n)-(4-2n)=-2$, thus it is an arithmetic sequence. $a_1=2$ $a_2=0$ $a_3=-2$ $a_4=-4$

In order for a sequence to be arithmetic, the difference of all consecutive terms must be constant. Hence here: $a_{n+1}-a_n=(4-2(n+1))-(4-2n)=(2-2n)-(4-2n)=-2$, thus it is an arithmetic sequence. $a_1=4-2(1)=2$ $a_2=4-2(2)=0$ $a_3=4-2(3)=-2$ $a_4=4-2(4)=-4$