Chapter 11 - Sequences; Induction; the Binomial Theorem - Section 11.1 Sequences - 11.1 Assess Your Understanding - Page 827: 39

$a_1=5 \\ a_2 =10 \\ a_3 =20 \\ a_4 =40 \\ a_5 =80$

We are given that $a_n=2 a_{n-1}$ and $a_1=5$. In order to determine the remaining values, we will have to substitute $n=2,3,4,5$ into the given sequence: $a_2= 2a_1=(2)(5)=10 \\ a_3=(2)(a_2) =(2)(10)=20 \\ a_4=(2)(a_3)=(2) (20)=40 \\ a_5=(2)(a_4)=(2)(40)=80$