Determine whether the sequence is arithmetic, geometric, both, or neither.
If the sequence is arithmetic, find d. If the sequence is geometric, find r.
81, -27, 9, -3,...
To determine if the sequence is arithmetic, look at the differences between successive terms.
81 – (-27) = 108
-27 – 9 = -36
The differences aren't all the same, so the sequence isn't arithmetic.
To determine if the sequence is geometric, look at the ratios between successive terms.
The ratios are all the same. This sequence is geometric with .