Hello, i have the following problem ...

f : P(N)$\displaystyle \rightarrow$$\displaystyle \overline{R}$ ... f(A)=$\displaystyle \sum_{n\in{A}}$$\displaystyle \frac{1}{3^n}$

Check if it is 1-1 at $\displaystyle R^+$ and at [0,1]

If anyone have an idea about this i will be thankfull