Answer:
Common difference(d) states that the difference between the two consecutive term of the arithmetic sequence
Given the sequence:
9, 2.5, -4, -10.5, -17
This is the arithmetic sequence with common difference
i.e, d = -6.5
Since,
2.5 - 9 = -6.5
-4-2.5 = -6.5
-10.5 -(-4) = -10.5 + 4 = -6.5
-17 + 10.5 = -6.5
Therefore, the common difference between successive terms in the given sequence is, -6.5