please check if I'm correct geometric sequences

please check if I'm correct.

 

1. enter the explicit rule for the geometric sequence 

9,6,4,8/3

 

my answer:

a_n = 9 • 2/3^n-1 

 

 

2.enter the recursive rule for the geometric sequence 

4,-16,64,-256

 

my answers:

a1= 4  a_n=4 • -4^n-1

 

3.the recursive rule for a geometric sequence is given

a₁=2/5; a_n =5a_n-1

 

enter the recursive rule for the sequence:

my answer: a_n=2/5 • 5^n-1

 

4. the explicit rule for a sequence is given

a_n=1/2(4/3)^n-1

 

enter the recursive rule for the geometric sequence 

my answer: a₁=1/2; a_n=4/3 • a_n-1