Answer:


Step-by-step explanation:
We are given that

We have to complete the recursive formula of f(n).
Substitute n=1






It forms geometric sequence because the ratio of two consecutive terms are equal.
Therefore, the recursive formula


Answer:

Step-by-step explanation:
It's 26×10×10×10 because there are 26 possibilities (a-z) for the first letter and 10 possibilities (0-9) for each number. That makes the answer 26,000.