Thực hiện các phép tính sau:
a) \(\dfrac{3x^2-3y^2}{5xy}.\dfrac{15x^2y}{2y-2x}\)
b) \(\dfrac{4a^2-3a+5}{a^3-1}-\dfrac{1-2a}{a^2+a+1}-\dfrac{6}{a-1}\)
c) \(\dfrac{2a^3-2b^3}{3a+3b}.\dfrac{6a+6b}{a^2-2ab+b^2}\)
d) \(x^2+1-\dfrac{x^4+1}{x^2+1}\)
e) \(\dfrac{3}{2x+6}-\dfrac{x-6}{2x^2+6x}\)