x-1/x的平方-3x+2-x+1/x的平方+3x+2-x的平方/x的平方-4
=x-1/(x-1)(x-2)-x+1/(x+1)(x+2)-x的平方/(x-2)(x+2)
=1/(x-2)-1/(x+2)-x平方/(x-2)(x+2)
=[x+2-(x-2)-x平方]/(x-2)(x+2)
=(4-x平方)//(x-2)(x+2)
=-(x-2)(x+2)/(x-2)(x+2)
=-1