a) 2/(х^2-2х) –x/(2x-4)=2/x(x-2)- x/2(x-2)=(4-x^2)/ 2x(x-2)=
(2-x)(2+x)/ -2x(2-x)=-(2+x)/2x;
b) x^2/(x^2-x+1) – 1/(x+1) +(2-x)/ (x^3+1)=
((x^2(x+1) – 1(x^2-x+1) +(2-x)) / (x+1)( x^2-x+1)=
= (x^3+
x^2-x^2-1+2-x) / (x+1)( x^2-x+1)= (x^3-x +1) / (x+1)( x^2-x+1)=1/(x+1)