Chapter 11 - Sequences; Induction; the Binomial Theorem - Section 11.3 Geometric Sequences; Geometric Series - 11.3 Assess Your Understanding - Page 844: 9

See answer below.

We need to substitute $1, 2, 3,$ and $4$ for $n$ into the given equation to find the first four terms. $s_1=(3)^1=3$ $s_2=(3)^2=9$ $s_3=(3)^3=27$ $s_4=(3)^4=(3)(3)(3)(3)=81$ We see that the the next term is equal to $3$ times the current term and this implies that the sequence is geometric with a common ratio of $3$.