In the given recursively defined arithmetic sequence, you have:
- \( a_1 = 4 \)
- \( a_n = a_{n-1} - 5 \)
The common difference \( d \) can be determined from the recursive formula:
- \( a_n = a_{n-1} - 5 \)
This indicates that each term is obtained by subtracting 5 from the previous term. Therefore, the common difference \( d \) is:
\( d = -5 \)
So, the common difference is \(-5\).