Give the recursive formula for the series 4,16,64...
0 solutions
16, the 2nd term, is 4 times the first term 4
64, the 3rd term, is 4 times the second term 16
So apparently,
Each term = 4 times the previous term
There are two acceptable ways to write that sentence
as a recursion formula:
If you think of it as
The nth term is 4 times the (n-1)st term
then the recursion formula is
an = 4·an-1, a1 = 4 where n > 1
Or if you think of it as
The (n+1)st term is 4 times the nth term
then the recursion formula is
an+1 = 4·an, a1 = 4 where n > 0
They are both correct, and equivalent.
Edwin
