Question

What is the common difference between successive terms in the sequence? 9, 2.5,-4, -10.5,-17,

Answer 1

6.5 is subtracted from each number.
9 - 6.5 = 2.5
2.5 - 6.5 = -4
-4 - 6.5 = -10.5
-10.5 - 6.5 = -17
or you could think of adding -6.5 to everything if that is easier for you to picture. 

Answer 2

Answer:

-6.5

Explanation: