What is the explicit rule for this geometric sequence? 4,45,425,4125,…

You did not write the question correctly but I will try to answer the question according to 2 possible interpretations of your question.

Case 1:

Given the geometric sequence:



Common ratio is given by

The explicit rule of a geometric sequence is given by

Therefore, the explicit rule of the given sequence is

Case 2:

Given the geometric sequence:



Common ratio is given by

The explicit rule of a geometric sequence is given by

Therefore, the explicit rule of the given sequence is