## Intermediate Algebra for College Students (7th Edition)

The solution set is $\{ -\frac{1}{2},\frac{1}{8},-\frac{1}{26},\frac{1}{80} \}$.
The given expression is $\frac{(-1)^n}{3^n-1}$ Plug $n=1$. $=\frac{(-1)^1}{3^1-1}$ $=\frac{-1}{3-1}$ $=-\frac{1}{2}$. Plug $n=2$. $=\frac{(-1)^2}{3^2-1}$ $=\frac{1}{9-1}$ $=\frac{1}{8}$. Plug $n=3$. $=\frac{(-1)^3}{3^3-1}$ $=\frac{-1}{27-1}$ $=-\frac{1}{26}$. Plug $n=4$. $=\frac{(-1)^4}{3^4-1}$ $=\frac{1}{81-1}$ $=\frac{1}{80}$.