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Determine if the following infinite sequences are geometric. If the sequence is geometric, provide the general term. Justify your decisions.

1. \(1, 5, 25, 125, …\)
   
   
2. \(15, - 15, 15, - 15, ...\)
   
   
3. \(16, 4, 1, \frac{1}{4}, ... \)
   
   
4. \(2, - 6, 24, - 120, ... \)