Question

what does the transformation $f(x) \mapsto 4f(x)$ do to the graph of $f(x)$?
reflects it across the x-axis
shrinks it vertically
reflects it across the y-axis
stretches it vertically

Explanation:

For a function transformation of the form $a f(x)$ where $a>1$, each $y$-value of the original function $f(x)$ is multiplied by $a$. This scales the graph outward from the x-axis, which is a vertical stretch. A vertical shrink occurs when $0

Answer:

stretches it vertically