The following rational equation has denominators that contain variables. For this equation, $a.$ Write the value or values of the variable that make a denominator zero. These are the restrictions on the variable. b$.$ Keeping the restrictions in mind, solve the equation.

$\frac{1}{x-2}-\frac{4}{x+4}=\frac{6}{x^2+2x-8}$

a$.$ What is$/$are the value or values of the variable that make$($s$)$ the denominators zero?

$x=$

$($Simplify your answer. Use a comma to separate answers as needed.$)$