Решение:

1. a) $$\frac{14p^4}{q^6} \cdot \frac{q^5}{56p^4} = \frac{14p^4q^5}{56p^4q^6} = \frac{14}{56} \cdot \frac{p^4}{p^4} \cdot \frac{q^5}{q^6} = \frac{1}{4q}$$
2. б) $$45a^3b \cdot \frac{c^2}{30a^4b} = \frac{45a^3bc^2}{30a^4b} = \frac{45}{30} \cdot \frac{a^3}{a^4} \cdot \frac{b}{b} \cdot c^2 = \frac{3c^2}{2a}$$
3. в) $$\frac{3a-9}{a+2} \cdot \frac{a^2-4}{a^2-9} = \frac{3(a-3)}{a+2} \cdot \frac{(a-2)(a+2)}{(a-3)(a+3)} = \frac{3(a-2)}{a+3}$$

Ответ:

1. a) $$\frac{1}{4q}$$
2. б) $$\frac{3c^2}{2a}$$
3. в) $$\frac{3(a-2)}{a+3}$$