2) x⁴y/28a * (-7a/x³y⁶);

2) $$\frac{x^4y}{28a} \cdot \left(-\frac{7a}{x^3y^6}\right) = - \frac{x^4y \cdot 7a}{28a \cdot x^3y^6} = - \frac{7ax^4y}{28ax^3y^6} = - \frac{x^{4-3}}{4y^{6-1}} = - \frac{x}{4y^5}$$

Ответ: -x/(4y⁵)