Answer
See below.
Work Step by Step
$y=4f(x)$ can be obtained by a vertical stretch with a factor of $4$ compared to $f(x)$, while $y=f(4x)$ can be obtained by a horizontal stretch with a factor of $\frac{1}{4}$ compared to $f(x)$. Thus one of them is a horizontal stretch, the other one is a vertical stretch and their factors are reciprocals.
