## Precalculus (6th Edition)

The graph of $y=\displaystyle \frac{4}{x-8}$ is obtained from the graph of $f(x)=\displaystyle \frac{1}{x}$ by shifting it right by 8 units, $f(x-8)$ and vertically stretching it by factor 4, $...4f(x-8)$. This graph passes the Horizontal Line Test, so the function is one-to-one