1)(a²+b²)/(a-b)(a+b) -(a+b)/(a-b)=(a²+b²-a²-2ab-b²)/(a²-b²)=2ab/(b²-a²)
2)(3a²+6a)/(a-3)(a+3) -2a/((a-3)=(3a²+6a-2a²-6a)/(a²-9)=a²/(a²-9)
3)(a-c)/c -(a-c)/(a+c)=(a²-c²-ac+c²)/c(a+c)=(a²-ac)/(ac+c²)
4)4a/1-(4a²-36)/(a+3)=(4a²+12a-4a²+36)/)a+3)=(12(a+3)/(a+3)=12