Exponential Models- Recursive Form

I'm confused on how to use recursive form, the directions talk about a(n+1) = a(n) x r... so confused on this! Please help,

Find the common ratio, write the recursive form, then find the next 3 terms in the geometric sequence:

1, 4, 16, 64

10, 100, 1000, 10000

128, 64, 32, 16

For the first sequence, the common ratio is 4/1 = 16/4 = 64/16 = 4. Therefore, the recursive form is

a(n+1) = 4 a(n)

so the next three terms are 64*4 = 256, 256*4 = 1024, and 1024*4 = 4096.

You should be able to do the other two. For the second sequence, the common ratio is 10 and for the third sequence, the common ratio is ½. The last terms you will find are 10000000 and 2.