Which formula represents the nnn-th term of a geometric sequence?
an=a1⋅rn−1a_n = a_1 \cdot r^{n-1}an=a1⋅rn−1
an=a1+(n−1)da_n = a_1 + (n-1)dan=a1+(n−1)d
an=a1⋅rna_n = a_1 \cdot r^nan=a1⋅rn
an=r⋅a1na_n = r \cdot a_1^nan=r⋅a1n