(2x-6)/(x²-4x+4)÷(12-4x)/(x²+x-6)*1/(x+3)=(2x-6)/(x²-4x+4)*(x²+x-6)/(12-4x)*1/(x+3)=2(x-3)/(x-2)²*(x+3)(x-2)/[4(3-x)]*1/(x+3)=2(x-3)/(x-2)*1/[2(3-x)]=-(x-3)/(x-2)*1/[2(x-3)]=-1/[2(x-2)]=-1/(2x-4)
