Ответ:

  1. \(\frac{a+4}{a^2}+\frac{a-2}{3a}=\frac{3(a+4)+a(a-2)}{3a^2}=\frac{a^2+a+12}{3a^2}\).
  2. \(\frac{3x}{x-1}+\frac{2x}{x+1}=\frac{3x(x+1)+2x(x-1)}{(x-1)(x+1)}=\frac{x(5x+1)}{x^2-1}\).
  3. \(\frac{x}{x-2y}-\frac{4y^2}{x^2-2xy}=\frac{x^2-4y^2}{x(x-2y)}=\frac{x+2y}{x}\).
  4. \(2a+b-\frac{4ab}{2a+b}=\frac{(2a+b)^2-4ab}{2a+b}=\frac{4a^2+b^2}{2a+b}\).
  5. \(\frac{4a}{a^2}+\frac{a-2}{3a}=\frac{12+ a-2}{3a}=\frac{a+10}{3a}\).
  6. \(\frac{3x}{x-1}+\frac{2x}{x+1}=\frac{x(5x+1)}{x^2-1}\).
  7. \(\frac{9x^2}{3xy-y^2}-\frac{y}{3x-y}=\frac{9x^2-y^2}{y(3x-y)}=\frac{3x+y}{y}\).
  8. \(a-3b+\frac{6ab}{a-3b}=\frac{(a-3b)^2+6ab}{a-3b}=\frac{a^2+9b^2}{a-3b}\).

Ответ: а) \(\frac{a^2+a+12}{3a^2}\); б) \(\frac{x(5x+1)}{x^2-1}\); в) \(\frac{x+2y}{x}\); г) \(\frac{4a^2+b^2}{2a+b}\); д) \(\frac{a+10}{3a}\); е) \(\frac{x(5x+1)}{x^2-1}\); ж) \(\frac{3x+y}{y}\); з) \(\frac{a^2+9b^2}{a-3b}\).