How do you find the asymptotes for f(x) = e^(-x) ?

Hence $x \to + \infty$ , $f \left(x\right) \to 0$ and $x \to - \infty$ is $f \left(x\right) \to + \infty$ and because ${e}^{-} x > 0$ the only asymptote is the horizontal axis yy'
The graph of $f$ is