Answer:
The common difference is 5.
Step-by-step explanation:
The reason why is because to get from -4 to -9 is the same -9-(-4), the reason I did that because your finding the difference I put the bracket is so its easier to read, but it is the same answer. To find the difference an easy way would just be to look at it as a non-negative so you would do 9-4 which is 5, so the answer is 5.