Which of the following is a geometric sequence?
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Answer:
A is an geometric sequence cause it is multiplying by -3 as it continues. So, as you are seeing below:
3*-3=-9
-9*-3=27
27*-3=-81
And for the other options , some of them were increasing and some were decreasing. They all are arithmetic sequence cause they all include common difference except A. A includes common ratio and that's why it's an geometric sequence.