#### Answer

(a) reflect $f(x)$ about the y-axis.
(b) stretch $f(x)$ vertically by a factor of 3

#### Work Step by Step

(a) We can obtain $f(-x)$ by reflecting the graph of $f(x)$ about the $y$-axis.
(b) We can obtain $3f(x)$ by stretching the graph of $f(x)$ vertically by a factor of 3.