Quy đồng mẫu thức các phân thức sau
a)\(\frac{3x+6}{x^2-4}\); \(\frac{5x}{x^2-2x}\); \(\frac{1-x}{x^2-3x+2}\)
b) \(\frac{1}{3x+3y}\); \(\frac{1}{2x+2y}\); \(\frac{1}{x^2+2xy+y^2}\)
c) \(\frac{4x^2-3x+5}{x^3-1}\) ; \(\frac{2x}{x^2+x+1}\); \(\frac{6}{x-1}\)
d) \(\frac{7}{5x}\); \(\frac{4}{x-2y}\); \(\frac{x-y}{8y^2-2x^2}\)
e) \(\frac{3x}{2x^2+6x}\); \(\frac{2x+6}{x^3+3x^2-9x-27}\)