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The common ratio of a geometric sequence is $r=-2$ and the product of the first two terms is $-98$.

Find all of the possible formulas for the $n$th term of the sequence. Select ALL that apply.

$a_{n}=7(-2)^{n-1}$

$a_{n}=-7(-2)^{n-1}$

$a_{n}=-7(2)^{n-1}$

$a_{n}=7(2)^{n-1}$

none of the above