(1\frac{2}{3}pv^3a)^2 = (\frac{5}{3}pv^3a)^2 = (\frac{5}{3})^2 \cdot p^2 \cdot (v^3)^2 \cdot a^2 = \frac{25}{9}p^2v^6a^2
Ответ: $$\frac{25}{9}p^2v^6a^2$$