## Algebra 1: Common Core (15th Edition)

You are given the sequence 20,15,10,5. The starting value is$a_{1}$=20. Find the common ratio by using the formula: R=$\frac{a2}{a1}$,R=$\frac{a4}{a3}$.Plug in the values to get the ratio: r=$\frac{15}{20}$=$\frac{3}{4}$ r=$\frac{5}{10}$=$\frac{1}{2}$ There is no common ratio. So the sequence is not geometric.