The given function is:
[tex]y=|x|[/tex]It is reflected across the x-axis to obtain a new function. This transformation follows the rule:
[tex]g(x)=-f(x)\rightarrow reflection\text{ }across\text{ }x-axis[/tex]If we apply this rule, we obtain:
[tex]y=-|x|[/tex]The answer is y=-|x|