Determine whether the sequence is arithmetic, geometric, both, or neither.
If the sequence is arithmetic, find d. If the sequence is geometric, find r.
100, 90, 80 , 70, ...
To determine if the sequence is arithmetic, look at the differences between successive terms.
90 – 100 = -10
80 – 90 = -10
70 – 80 = -10
The differences are all the same. The sequence is arithmetic with
d = -10.
To determine if the sequence is geometric, look at the ratios between successive terms.
The ratios aren't all the same, so the sequence isn't geometric.