In a recursively defined arithmetic sequence, the common difference can be found from the recursive formula.
Here, the sequence is defined as:
- \( a_1 = 4 \)
- \( a_n = a_{n-1} - 5 \)
The common difference \( d \) is the value that is added (or subtracted in this case) to get from one term to the next. In this case, we see that \( a_n \) is formed by subtracting 5 from the previous term \( a_{n-1} \).
Thus, the common difference is: \[ d = -5 \]
So, the common difference is \(-5\).