1. 8,16,32, 64, 128

multiply terms by 2

soltuon:

an=a1r^n-1

=8(2)^4-1

=8(8)

a4=64

an=a1r^n-1

=8(2)^5-1

=8(16)

a5=128

2. 120,60,30,15, 15/2

multiply terms by 1/2

solution:

an=a1r^n-1

=120(1/2)^4-1

=120(1/8)

a4=15

an=a1r^n-1

=120(1/2)^5-1

=120(1/16)

a4=15/2