Представьте выражение в виде дроби:

1. а) $$\frac{28p^4}{q^6} \cdot \frac{q^5}{56p^4}$$ $$\frac{28p^4}{q^6} \cdot \frac{q^5}{56p^4} = \frac{28}{56} \cdot \frac{p^4}{p^4} \cdot \frac{q^5}{q^6} = \frac{1}{2} \cdot 1 \cdot \frac{1}{q} = \frac{1}{2q}$$
2. б) $$\frac{72x^3y}{z} : (30x^2y)$$ $$\frac{72x^3y}{z} : (30x^2y) = \frac{72x^3y}{z} \cdot \frac{1}{30x^2y} = \frac{72}{30} \cdot \frac{x^3}{x^2} \cdot \frac{y}{y} \cdot \frac{1}{z} = \frac{12}{5} \cdot x \cdot 1 \cdot \frac{1}{z} = \frac{12x}{5z}$$
3. в) $$\frac{x^2-1}{x^2-9} : \frac{5x+10}{x-1}$$ $$\frac{x^2-1}{x^2-9} : \frac{5x+10}{x-1} = \frac{(x-1)(x+1)}{(x-3)(x+3)} \cdot \frac{x-1}{5(x+2)} = \frac{(x-1)^2(x+1)}{5(x-3)(x+3)(x+2)}$$
4. г) $$\frac{y+c}{c} \cdot (\frac{c}{y} + \frac{c}{y+c})$$ $$\frac{y+c}{c} \cdot (\frac{c}{y} + \frac{c}{y+c}) = \frac{y+c}{c} \cdot (\frac{c(y+c) + cy}{y(y+c)}) = \frac{y+c}{c} \cdot (\frac{cy + c^2 + cy}{y(y+c)}) =$$ $$\frac{y+c}{c} \cdot \frac{2cy + c^2}{y(y+c)} = \frac{y+c}{c} \cdot \frac{c(2y + c)}{y(y+c)} = \frac{2y+c}{y}$$