Explanation of function $|y| = x$ First time posting here.
Studying this book and this statement came across.

In the equation $|y| = x$, $y$ is not a function of $x$ because every nonnegative $x$-value has two $y$-values. For example, if $x = 3$, $|y| = 3$ has the solutions $y = 3$ and $y = -3$.
Huettenmueller, Rhonda. College algebra demystified. New York: McGraw-Hill Professional, 2014.

So far, I never saw operations on $y$ side of the equation. How can I solve those ?
Thanks in advance

Let observe that by definition $|y|=x \implies x\ge 0$ and


*

*$y\ge 0 \implies |y|=x \iff y=x$

*$y< 0 \implies |y|=x \iff -y=x \iff y=-x$
then we have two different function both defined for not negative $x$ values.
Plot of |y|=x
