2. Выполнить действия a) $$\frac{25x^7y^6}{y^3} \cdot \frac{15x^8}{}$$; б) $$\frac{30m^2}{n} : (6mn)$$; в) $$\frac{7x+7y}{a^4} \cdot \frac{6a^5}{x^2-y^2}$$

а) $$\frac{25x^7y^6}{y^3} \cdot \frac{15}{x^8} = \frac{25 \cdot 15 x^7 y^6}{x^8 y^3} = \frac{375y^3}{x}$$; б) $$\frac{30m^2}{n} : (6mn) = \frac{30m^2}{n} \cdot \frac{1}{6mn} = \frac{30m^2}{6mn^2} = \frac{5m}{n^2}$$; в) $$\frac{7x+7y}{a^4} \cdot \frac{6a^5}{x^2-y^2} = \frac{7(x+y)}{a^4} \cdot \frac{6a^5}{(x-y)(x+y)} = \frac{7 \cdot 6 a^5 (x+y)}{a^4 (x-y)(x+y)} = \frac{42a}{x-y}$$