Выполни деление

\(\dfrac {y^2 + y^4}{8z^3} : \dfrac {2y+2y^3}{5z} = \dfrac{y^2(1+y^2) \cdot 5z}{8z^3 \cdot 2y(1+y^2)} = \dfrac {5y}{16z^2} \) .

а) \(\dfrac {5a-10a^2}{2b^2} : \dfrac {7a^2 - 14a^3}{3b^5} = \) [ ];

б) \(\dfrac {2a^2 - 4a + 1}{3b-6} : \dfrac{3-12a+6a^2}{5b-10} = \) [ ];

в) \(\dfrac {1+2c^2}{d^2 - d} : \left(- \dfrac {6c^5 + c^3}{1-d}\right) = \) [ ];

г) \(\dfrac {x^2-x^3}{5y-10} : \dfrac {2x^5-2x^6}{2-y} = \) [ ].