Ответ:

  1. \(\dfrac{2xy^3}{8x^2y^2}=\dfrac{2xy^2\cdot y}{2xy^2\cdot4x}=\dfrac{y}{4x}\), при \(x\ne0, y\ne0\).
  2. \(\dfrac{3x^2+9x}{3x}=\dfrac{3x(x+3)}{3x}=x+3\), при \(x\ne0\).
  3. \(\dfrac{a-3}{a^2-6a+9}=\dfrac{a-3}{(a-3)^2}=\dfrac1{a-3}\), при \(a\ne3\).

Ответ: а) \(\dfrac{y}{4x}\); б) \(x+3\); в) \(\dfrac1{a-3}\).