Answer
The equation defines $y$ as a function of $x$.
The function can be written as $f(x)=2|x|$.
Work Step by Step
Solve for $y$ in terms of $x$ to have:
$y=-2|x|$
This equation is a rule that gives one value of $y$ for each value of $x$ so the equation defines $y$ as a function of $x$.
The function can be written as $f(x)=2|x|$.
