6a 6) 35c5 14c2

6) $$\frac{6a}{35c^5} - \frac{9b}{14c^2} = \frac{126ac^2}{490c^7} - \frac{441bc^5}{490c^7} = \frac{126ac^2 - 441bc^5}{490c^7}$$

Ответ: $$\frac{126ac^2 - 441bc^5}{490c^7}$$