Answer
The explicit formula is $a_{n}$=686 $\times$ ($\frac{1}{7}$$)^{n-1}$
Work Step by Step
You have to use the explicit formula. The explicit formula is
$a_{n}$=$a_{1}$ $\times$ (r$)^{n-1}$.
The starting value is 686 so it is $a_{1}$.
You have the sequence 686,98,14 so use the common ratio formula(r=$\frac{{a_{2}}}{{a_{1}}}$) r=$\frac{686}{98}$=$\frac{1}{7}$ and r=$\frac{98}{14}$=$\frac{1}{7}$.So the common ratio is $\frac{1}{7}$.Substitute the value of a1 and R into the explicit formula:
The explicit formula is $a_{n}$=686 $\times$ ($\frac{1}{7}$$)^{n-1}$
