Выполните действия: a) $$\frac{5}{x-2} - \frac{4x-7}{x-2}$$ б) $$\frac{5}{8x^5} - \frac{3}{6x^3}$$ в) $$\frac{54x^2y^5}{25a^4b^2} \cdot (-\frac{70a^7b^6}{63x^3y^3})$$ г) $$\frac{x^2+5x}{12x^6} : \frac{x^2-25}{6x^{12}}$$ д) $$(-\frac{3m^5}{5n^2})^3$$

a) $$\frac{5}{x-2} - \frac{4x-7}{x-2} = \frac{5-(4x-7)}{x-2} = \frac{5-4x+7}{x-2} = \frac{12-4x}{x-2} = \frac{-4(x-3)}{x-2}$$ б) $$\frac{5}{8x^5} - \frac{3}{6x^3} = \frac{5}{8x^5} - \frac{1}{2x^3} = \frac{5}{8x^5} - \frac{4x^2}{8x^5} = \frac{5-4x^2}{8x^5}$$ в) $$\frac{54x^2y^5}{25a^4b^2} \cdot (-\frac{70a^7b^6}{63x^3y^3}) = - \frac{54x^2y^5 \cdot 70a^7b^6}{25a^4b^2 \cdot 63x^3y^3} = - \frac{6 \cdot 7 a^3b^4y^2}{5 \cdot 7x} = - \frac{6a^3b^4y^2}{5x}$$ г) $$\frac{x^2+5x}{12x^6} : \frac{x^2-25}{6x^{12}} = \frac{x(x+5)}{12x^6} \cdot \frac{6x^{12}}{(x-5)(x+5)} = \frac{x \cdot 6x^{12}}{12x^6 \cdot (x-5)} = \frac{x^7}{2(x-5)}$$ д) $$(-\frac{3m^5}{5n^2})^3 = - \frac{(3m^5)^3}{(5n^2)^3} = - \frac{27m^{15}}{125n^6}$$