(x+2/x^2-2x)-(x-1/x^2-4x+4)/(4-x/x) =((x+2)/[x(x-2)]-((x-1)/(x-2)^2)/[(4-x)/x]=[(x^2-4)-x(x-1)]/[x(x-2)^2]/[(4-x)/x]=(x-4)/{x(x-2)^2]* x/(4-x)=-1/(x-2)^2
