Question

Write an explicit rule for the geometric sequence 4, 8, 16, 32, ..

Answer 1

8÷4=2
16÷8=2
32÷16=2
multiply by 2

Answer 2

First term:  a(1) = 4; common ratio:  r = 2

Then:

a(n) = 4(2)^(n-1)

Check:  Predict the 4th term using this formula:

a(4) = 4(2)^3 = 4(8) = 32  (correct)