Answer
Reflect the graph of $y=f(x)$ with respect to $x$ axis and then stretch it vertically by the factor of $3$.
Work Step by Step
We start with the graph $y=f(x)$. First reflect the graph if this function with respect to $x$ to get the graph of $y=-f(x)$. Then increase the value of the function at every $x$ three times i.e. stretch the graph vertically by the factor of $3$.