2x²-4x/x+2·x²+2x/x²-4x+4+4x/2-x
=2x(x-2)/(x+2)× x(x+2)/(x-2)²-4x/(x-2)
=2x²/(x-2)-4x/(x-2)
=(2x²-4x)/(x-2)
=2x
当x=1/2时
原式=1