Given the recursive formula for a geometric sequence, identify the common ratio and determine the explicit formula. \begin{aligned} &\text { 1) } a_{n}=a_{n-1} \cdot 6\\ &a_{1}=2 \end{aligned} \begin{array}{l} \text {

2) } a_{n}=a_{n-1} \cdot-2 \\ a_{1}=2 \end{array} \begin{array}{l} \text { 3) } a_{n}=a_{n-1} \cdot 4 \\ a_{1}=4 \end{array} \text { 4) } \begin{array}{l} a_{n}=a_{n-1} \cdot-6 \\ a_{1}=-2 \end{array}