If a sequence ana_nan is defined by an=2n⋅31−na_n = 2^n \cdot 3^{1-n}an=2n⋅31−n, which of the following is true?
It is an arithmetic sequence
It is a geometric sequence with r=2/3r=2/3r=2/3
It is a geometric sequence with r=3/2r=3/2r=3/2
It is neither