Final answer:
The common difference between successive terms in the sequence is -6.5
Step-by-step explanation:
The common difference between successive terms in a sequence is the difference between any two consecutive terms in the sequence. To find the common difference, subtract the second term from the first term, and then subtract the third term from the second term, and so on.
In the given sequence, the common difference can be found by subtracting each term from the previous term:
2.5 - 9 = -6.5
-4 - 2.5 = -6.5
-10.5 - (-4) = -6.5
-17 - (-10.5) = -6.5
So, the common difference between successive terms in the sequence is -6.5.