Visual proof that $\lim_{x\to \infty} \frac{x^r}{a^x} = 0$ I am looking for a visual proof (in this sense: https://mathoverflow.net/questions/8846/proofs-without-words) for the fact that 
$$
    \lim_{x\to \infty} \frac{x^r}{a^x}  = 0
$$
($r > 0,a>1$)
Or at least for a simple (high school level) argument that makes this relation plausible (but it doesn't have to be a rigerous mathematical proof - I know to proof it rigerously, but that's not what I am looking for).

Every time $x$ increases by $1$, the bottom gets multiplied by $a$ and the top gets multiplied by $$\left(\frac{x+1}{x}\right)^r = \left(1+\frac{1}{x}\right)^r \approx 1+\frac{r}{x}$$
So the bottom keeps growing by the same factor while the factor that the top grows by gets smaller and smaller, and will eventually get smaller than $a$. In the long run (i.e. as $x \to\infty$) the bottom will win out, driving the whole expression to $0$. (This does make an appeal to a binomial theorem approximation.)
It's not intuitive, and probably doesn't have the "Aha!" appeal of a visual proof, but I think it would help high schoolers start to think about comparing different rates of growth and help them build their intuition.
And if I were presenting this to high schoolers I would definitely start off showing how it worked in a specific simple example, like $\frac{x^2}{2^x}$. Write ten terms of $x^2$, note that they're increasing, but then write ten terms of $2^x$ and note how the crush the terms on the top. Then make the generalization, and maybe note that if $a$ is close to $1$ and $r$ is large it will take more terms for the bottom to win, but it will eventually, and we are going to $\infty$.
