Chapter 11 - Sequences; Induction; the Binomial Theorem - Section 11.1 Sequences - 11.1 Assess Your Understanding - Page 827: 40

$a_1=2 \\ a_2= -2 \\ a_3=2 \\ a_4 =-2 \\ a_5 =2$

We are given that $a_n=- a_{n-1}$ and $a_1= 2$. In order to determine the remaining values, we will have to substitute $n=2,3,4,5$ into the given sequence: $a_2= -a_1=-(2)=-2 \\ a_3=-a_2 =-(-2)=2 \\ a_4=-a_3=-(2)=-2 \\ a_5=-a_4=-(-2)=2$