(x^2-2x)/(x^2-4)÷[-2-(2x-4)/(x+2)]
=[x(x-2)/(x+2)(x-2)]÷[(-2x-4-2x+4)/(x+2)]
=x/(x+2)÷(-4x)/(x+2)
=x/(x+2)×(x+2)/(-4x)
=-1/4