1. Представьте в виде дроби: a) $$\frac{56x^3y^4}{z^5} \cdot (-\frac{x^2z^4}{16y^6})$$; б) $$\frac{35m^8n^5}{48p^4q^{12}} : \frac{70m^7n^6}{9p^3q^{14}}$$; в) $$\frac{72a^7b^{16}}{c^{10}} : (24a^3b^{16}c^8)$$; г) $$\frac{mn}{m^2-n^2} \cdot (\frac{m+7}{m} - \frac{n+7}{n})$$; д) $$\frac{a-2}{a^2} \cdot \frac{ab-a}{a-2} + \frac{2-b}{2a}$$; e) $$\frac{3b-3c}{c} \cdot \frac{4c^2}{b^2-c^2}$$

a) $$\frac{56x^3y^4}{z^5} \cdot (-\frac{x^2z^4}{16y^6}) = -\frac{56x^5y^4z^4}{16y^6z^5} = -\frac{7x^5}{2y^2z}$$

б) $$\frac{35m^8n^5}{48p^4q^{12}} : \frac{70m^7n^6}{9p^3q^{14}} = \frac{35m^8n^5}{48p^4q^{12}} \cdot \frac{9p^3q^{14}}{70m^7n^6} = \frac{35 \cdot 9 \cdot m^8 \cdot n^5 \cdot p^3 \cdot q^{14}}{48 \cdot 70 \cdot p^4 \cdot q^{12} \cdot m^7 \cdot n^6} = \frac{3 \cdot m \cdot q^2}{32 \cdot p \cdot n} = \frac{3mq^2}{32pn}$$

в) $$\frac{72a^7b^{16}}{c^{10}} : (24a^3b^{16}c^8) = \frac{72a^7b^{16}}{c^{10}} \cdot \frac{1}{24a^3b^{16}c^8} = \frac{72a^7b^{16}}{24a^3b^{16}c^{10}c^8} = \frac{3a^4}{c^{18}}$$

г) $$\frac{mn}{m^2-n^2} \cdot (\frac{m+7}{m} - \frac{n+7}{n}) = \frac{mn}{m^2-n^2} \cdot (\frac{n(m+7)-m(n+7)}{mn}) = \frac{mn}{m^2-n^2} \cdot (\frac{nm+7n-nm-7m}{mn}) = \frac{mn}{m^2-n^2} \cdot \frac{7(n-m)}{mn} = \frac{7(n-m)}{(m-n)(m+n)} = -\frac{7}{m+n}$$

д) $$\frac{a-2}{a^2} \cdot \frac{ab-a}{a-2} + \frac{2-b}{2a} = \frac{(a-2) \cdot a \cdot (b-1)}{a^2 \cdot (a-2)} + \frac{2-b}{2a} = \frac{a(b-1)}{a^2} + \frac{2-b}{2a} = \frac{b-1}{a} + \frac{2-b}{2a} = \frac{2(b-1)+2-b}{2a} = \frac{2b-2+2-b}{2a} = \frac{b}{2a}$$

e) $$\frac{3b-3c}{c} \cdot \frac{4c^2}{b^2-c^2} = \frac{3(b-c)}{c} \cdot \frac{4c^2}{(b-c)(b+c)} = \frac{3 \cdot 4c^2 \cdot (b-c)}{c \cdot (b-c) \cdot (b+c)} = \frac{12c}{b+c}$$