a,\(\dfrac{2}{x-2}\)-\(\dfrac{2}{x^2-x-2}\).(1+\(\dfrac{3x+x^2}{x+3}\))
b,\(\dfrac{2}{xy}\):(\(\dfrac{1}{x}\)-\(\dfrac{1}{y}\))-\(\dfrac{x^2-y^2}{\left(x-y\right)^2}\)
c,(\(\dfrac{x+y}{2x-2y}\)-\(\dfrac{x-y}{2x+2y}\)-\(\dfrac{2y^2}{y^2-x^2}\)):\(\dfrac{2y}{x-y}\)