[1/(x²-2x)-1/(x²-4x+4)]÷[2/(x²-2x)]
=[1/x(x-2)-1/(x-2)²]×[x(x-2)/2]
=1/x(x-2)×[x(x-2)/2]-1/(x-2)²×[x(x-2)/2]
=1/2-x/2
=(1-x)/2