1214. Преобразуйте выражение: a) $$\frac{13x^{-2}}{y} \cdot \frac{y^{12}}{39x^{-3}}$$; б) $$\frac{5a^5}{b^{-7}} \cdot \frac{7b^{-3}}{25a}$$; в) $$\frac{p}{3c^{-2}} \cdot \frac{15c}{p^{-2}}$$; г) $$\frac{26x^{17}}{y^{-8}} \cdot \frac{y}{13x^{25}}$$

a) $$\frac{13x^{-2}}{y} \cdot \frac{y^{12}}{39x^{-3}} = \frac{13}{39} \cdot \frac{x^{-2}}{x^{-3}} \cdot \frac{y^{12}}{y} = \frac{1}{3}xy^{11}$$ б) $$\frac{5a^5}{b^{-7}} \cdot \frac{7b^{-3}}{25a} = \frac{5 \cdot 7}{25} \cdot \frac{a^5}{a} \cdot \frac{b^{-3}}{b^{-7}} = \frac{7}{5}a^{4}b^{4}$$ в) $$\frac{p}{3c^{-2}} \cdot \frac{15c}{p^{-2}} = \frac{15}{3} \cdot \frac{p}{1} \cdot \frac{1}{p^{-2}} \cdot \frac{c}{c^{-2}} = 5p^{3}c^{3}$$ г) $$\frac{26x^{17}}{y^{-8}} \cdot \frac{y}{13x^{25}} = \frac{26}{13} \cdot \frac{x^{17}}{x^{25}} \cdot \frac{y}{y^{-8}} = 2x^{-8}y^{9} = \frac{2y^9}{x^8}$$