（x+2/x^2-2x-x-1/x^2-4x+4）/x-4/x
=[(x+2)/x(x-2)-(x-1)/(x-2)²]／(x-4)/x
=[(x²-4-x²+x)/x(x-2)²]×x/(x-4)
=[(x-4)/x(x-2)²]*[x/(x-4)]
=1/(x-2)²
=1/(2-√5-2)²
=1/5