How to have a negative exponential function whose asymptote is 0?

Question

So, I need an exponential function on the form $e^{-ax}$ that is 1 at $x=0$ and approaches $0.3$ as $x \rightarrow \infty$. I tried doing $e^{-ax} + 0.3$, but that only lead to the function starting at $1.3$ (although it did approach $0.3$ as $x \rightarrow \infty$)

The answer is probably really simple but I can't seem to figure it out.

Answer 1

Choose the function $$f(x)=0.3+0.7e^{-x}$$

Answer 2

Multiply $e^{-ax}$ by $0.7$. So, consider $0.7e^{-ax}+ 0.3$.