4 (-b4)5. (3b2)4 - (2xy)² (-2x)²

4) A: $$(-b^4)^5 \cdot (3b^2)^4 = -b^{20} \cdot 81b^8 = -81b^{20+8} = -81b^{28}$$

B: $$-(2xy)^2 \cdot (-2x)^2 = -4x^2y^2 \cdot 4x^2 = -16x^{2+2}y^2 = -16x^4y^2$$

Ответ: A: $$-81b^{28}$$, B: $$-16x^4y^2$$