Answer
Vertical scale by a factor of 3, reflect across the $x$-axis
Work Step by Step
We are given the function:
$g(x)=-3x^2$
We start with the parent function $p(x)=x^2$.
First vertically scale $p(x)$ by a factor of 3 to get the function $h(x)=3x^2$.
Then reflect the function $h(x)$ across the $x$-unit to get the function $g(x)=-3^2$.
Graph all transformations: