X-y/x+y-y/x-y 3b^2+2b/b^2-4-b/b-2 3a^2+6a/a^2-9-2a/a-3

1)(x-y)/(x+y) -y/(x-y)=(x²-2xy+y²-xy-y²)/(x²-y²)=(x²-3xy)/(x²-y²)
2)(3b²+2b)/(b-2)(b+2) -b/(b-2)=(3b²+2b-b²-2b)/(b²-4)=2b²/(b²-4)
3)(3a²+6a)/(a-3)(a+3) - 2a/(a-3)=(3a²+6a-2a²-6a)/(a-3)(a+3)=a²/(a²-9)