Determine if equation represents y as function of x

Question

what is the process to determine whether or not the equation represents y as a function of x

x² = y²

Answer 1

If y is a function of x, then every x-value input will produce only one y-value output.

So, let's think about it. If I say x = -2, then (-2)² = 4. Since y being either -2 or 2 would make the right side equal 4, we do NOT have a function.