Tính: a) \(\frac{1-2x}{6x^3y} + \frac{3+2y}{6x^3y} + \frac{2x-4}{6x^3y};\) b) \(\frac{3x+5}{4y^3} - \frac{5-15x}{4y^3};\) c) \(\frac{xy}{x^2 - y^2} - \frac{x^2}{y^2 - x^2};\) d) \(\frac{3}{2x+6} - \frac{x-6}{2x^2+6x};\) e) \(\frac{x+1}{x-3} - \frac{1-x}{x+3} - \frac{2x(1-x)}{9-x^2};\) f) \(\frac{1}{x^2-x+1} + \frac{1-x^2+2}{x^3+1};\) g) \(\frac{3x+1}{(x-1)^2} + \frac{1}{x+1} + \frac{x+3}{1-x^2};\) h)